Heightened mortality after the death of a spouse: Marriage protection or marriage selection?

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Journal of Health Economics 27 (2008) 1326–1342 Contents lists available at ScienceDirect Journal of Health Economics journal homepage: www.elsevier.com/locate/econbase Heightened mortality after the death of a spouse: Marriage protection or marriage selection? Javier Espinosa a,, William N. Evans b,c a Department of Economics, Rochester Institute of Technology, Rochester, NY 14623, USA b Department of Economics and Econometrics, University of Notre Dame, Notre Dame, IN 46556, USA c National Bureau of Economic Research, 1050 Massachusetts Avenue, Cambridge, MA 02138-5398, USA article info Article history: Received 18 July 2007 Received in revised form 27 March 2008 Accepted 3 April 2008 Available online 11 April 2008 JEL classification: I12 J12 Keywords: Mortality Marriage Widow abstract We test whether the heightened mortality after the death of a spouse represents correla- tion or causation by examining the heterogeneity in the bereavement effect based on the spouse’s cause of death. Some causes of death are correlated with socioeconomic charac- teristics while others are not. Equality in the bereavement effect across these two types of death would signal a causal relationship while no bereavement effect for uncorrelated causes of death would indicate an omitted variables bias. Results indicate that the observed effect for women is subject to an omitted variables bias but the estimates for men indicate a causal relationship. © 2008 Elsevier B.V. All rights reserved. 1. Introduction In recent years, legislators at the federal and state level have proposed a variety of “healthy marriage” laws designed to discourage divorce and encourage couples with children or pregnant couples to marry. In early January 2005, for example, a welfare reauthorization bill (HR 240) was introduced in the House of Representatives 1 that included over $300 million in funds for healthy marriage education and research. Behind these initiatives is the belief that marriage improves the lives of husbands, wives, children and communities. This belief is bolstered by research from a variety of disciplines that documents the social and economic outcomes of the married are better along many dimensions than those who are single (Waite and Gallagher, 2000). Married people, for example, have higher wages (Korenman and Neumark, 1991; Schoeni, 1995), higher incomes (Lerman, 2002), lower rates of poverty (Sawhill and Thomas, 2002), accumulate more wealth (Lupton and Smith, 2003), report higher levels of happiness (Diener et al., 2000; Stack and Eshleman, 1998; Taylor et al., 2006) are less susceptible to psychological disorders (Gove et al., 1983; Barrett, 2000; Quirouette and Gold, 1992), are less prone to suicide (Smith et al., 1988; Kachur et al., 1995; Luoma and Pearson, 2002) and are less likely to be involved in criminal activity (Laub et al., 1998), compared with singles. Researchers have also documented a potential health benefit of marriage—married people have a longer life expectancy than the non-married (Gove, 1973; Kobrin and Hendershot, 1977; Smith and Waitzman, 1994; Hu and Goldman, 1990). Scholars have titled this relationship ‘marriage protection’. Some of the most convincing evidence consistent Corresponding author. Tel.: +1 585 475 5872; fax: +1 585 475 7120. E-mail addresses: [email protected] (J. Espinosa), [email protected] (W.N. Evans). 1 HR 240. Personal Responsibility, Work, and Family Promotion Act of 2005. January 4, 2005. Section 103.b.2.C. 0167-6296/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jhealeco.2008.04.001

Transcript of Heightened mortality after the death of a spouse: Marriage protection or marriage selection?

Page 1: Heightened mortality after the death of a spouse: Marriage protection or marriage selection?

Journal of Health Economics 27 (2008) 1326–1342

Contents lists available at ScienceDirect

Journal of Health Economics

journa l homepage: www.e lsev ier .com/ locate /econbase

Heightened mortality after the death of a spouse:Marriage protection or marriage selection?

Javier Espinosaa,∗, William N. Evansb,c

a Department of Economics, Rochester Institute of Technology, Rochester, NY 14623, USAb Department of Economics and Econometrics, University of Notre Dame, Notre Dame, IN 46556, USAc National Bureau of Economic Research, 1050 Massachusetts Avenue, Cambridge, MA 02138-5398, USA

a r t i c l e i n f o

Article history:Received 18 July 2007Received in revised form 27 March 2008Accepted 3 April 2008Available online 11 April 2008

JEL classification:I12J12

Keywords:MortalityMarriageWidow

a b s t r a c t

We test whether the heightened mortality after the death of a spouse represents correla-tion or causation by examining the heterogeneity in the bereavement effect based on thespouse’s cause of death. Some causes of death are correlated with socioeconomic charac-teristics while others are not. Equality in the bereavement effect across these two typesof death would signal a causal relationship while no bereavement effect for uncorrelatedcauses of death would indicate an omitted variables bias. Results indicate that the observedeffect for women is subject to an omitted variables bias but the estimates for men indicatea causal relationship.

© 2008 Elsevier B.V. All rights reserved.

1. Introduction

In recent years, legislators at the federal and state level have proposed a variety of “healthy marriage” laws designed todiscourage divorce and encourage couples with children or pregnant couples to marry. In early January 2005, for example,a welfare reauthorization bill (HR 240) was introduced in the House of Representatives1 that included over $300 million infunds for healthy marriage education and research. Behind these initiatives is the belief that marriage improves the lives ofhusbands, wives, children and communities. This belief is bolstered by research from a variety of disciplines that documentsthe social and economic outcomes of the married are better along many dimensions than those who are single (Waite andGallagher, 2000). Married people, for example, have higher wages (Korenman and Neumark, 1991; Schoeni, 1995), higherincomes (Lerman, 2002), lower rates of poverty (Sawhill and Thomas, 2002), accumulate more wealth (Lupton and Smith,2003), report higher levels of happiness (Diener et al., 2000; Stack and Eshleman, 1998; Taylor et al., 2006) are less susceptibleto psychological disorders (Gove et al., 1983; Barrett, 2000; Quirouette and Gold, 1992), are less prone to suicide (Smith et al.,1988; Kachur et al., 1995; Luoma and Pearson, 2002) and are less likely to be involved in criminal activity (Laub et al., 1998),compared with singles. Researchers have also documented a potential health benefit of marriage—married people have alonger life expectancy than the non-married (Gove, 1973; Kobrin and Hendershot, 1977; Smith and Waitzman, 1994; Hu andGoldman, 1990). Scholars have titled this relationship ‘marriage protection’. Some of the most convincing evidence consistent

∗ Corresponding author. Tel.: +1 585 475 5872; fax: +1 585 475 7120.E-mail addresses: [email protected] (J. Espinosa), [email protected] (W.N. Evans).

1 HR 240. Personal Responsibility, Work, and Family Promotion Act of 2005. January 4, 2005. Section 103.b.2.C.

0167-6296/$ – see front matter © 2008 Elsevier B.V. All rights reserved.doi:10.1016/j.jhealeco.2008.04.001

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with the marriage protection hypothesis demonstrates a heightened mortality rate for survivors in the years just after thedeath of their spouse (Kaprio et al., 1987; Schaefer et al., 1995). One interpretation of the data suggests that as the marriage isended by death of a spouse, the protective effects of marriage are eroded and the health of the survivor is then compromised.

There is, however, an alternative hypothesis called marriage selection (Hu and Goldman, 1990; Goldman, 1993; Waldronet al., 1996; Cheung, 1998; Murray, 2000) that may explain the better health outcomes of married individuals and why wewitness a temporal correlation in spousal mortality. In a marriage market where potential husbands and wives find oneanother, there is a selection process that underlies the matching of two people (Becker, 1973, 1974). Much of the empiricalwork about marriage markets demonstrates positive assortative mating, which is the occurrence of mating between similarindividuals at higher than random frequencies. Given the importance health habits have on life expectancy and mortality(McGinnis and Foege, 1993) and the similarity in health investments by spouses (documented in Section 2 below), we wouldexpect to see life expectancy patterns among the married converge as well.

In this article, we estimate the impact of spousal death on the surviving spouse’s mortality, what some researchers havecome to call the “bereavement effect”. We do so by trying to extract information about the survivor’s mortality based onthe cause of death for their spouse. The starting point for our analysis is the fact that some deaths reveal more informationabout the surviving spouse than others. Deaths from cirrhosis of the liver, heart disease, and lung cancer are causes that arecorrelated with various measures of socioeconomic status (SES) and hence, because of assortative mating, characteristics ofthe surviving spouse. Therefore, any heightened mortality among survivors after the spouse dies from one of these causesis potentially contaminated by an omitted variables bias. In contrast, if some deaths are random in the population, thenthe fact that a spouse dies from one of these causes should not reveal any information about the survivor. Hence, anybereavement effect that occurs after the death of a spouse from these uninformative causes is more likely to be causal. Whilewe cannot identify which causes of death are ‘random’, we can identify those that are uncorrelated with important observedcharacteristics. For example, as we document below, some causes of death like adult leukemia and other forms of cancer areuncorrelated with measures of SES like income, education and occupation. Therefore, if the bereavement effect is presentafter a spouse dies from one of these causes of death, we are more confident that the result is driven by marriage protectionrather than a byproduct of marriage selection.

To implement this idea, we use a public-use version of the National Longitudinal Mortality Survey (NLMS) to createlongitudinal data sets of married couples, aged 50–70. We identify those causes of death that are predicted by SES such asincome, education and occupation, and those that are not. We label these two types of deaths as informative and uninforma-tive causes of death, respectively.2 In mortality models that are estimated via Cox proportional hazards, if the bereavementeffect is entirely a product of marriage selection, we should find the magnitude of the bereavement effect resulting fromuninformative causes of spousal death to be substantially smaller than the magnitude of the effect for informative causes.In contrast, if marital protection explains all of the bereavement effect, then the impacts of informative and uninformativedeaths should be similar in magnitude.

In Section 2, we summarize the literature on both marriage and mortality and the bereavement effect. We also presentsome data indicating the robust correlation in health behaviors among older married couples, a result that raises the suspicionthat the bereavement effect is driven by marriage selection. In Section 3, we introduce the NLMS, outline the Cox proportionalhazard model, and introduce the procedure to isolate what are informative and uninformative deaths. The results from thesemodels are not surprising. Among men, causes of death like pancreatic cancer, genital cancers, and leukemia are considereduninformative while for women, the list includes breast cancer and genitourinary cancer, among others. In Section 4, wedemonstrate that for men, the bereavement effect is large whether their wife dies from an informative or uninformativecase, suggesting the heightened mortality after the death of a spouse is due to marriage protection. In contrast, for women,we find no bereavement effect for uninformative causes of death, but a large and statistically precise effect for informativecauses, suggesting most of the bereavement effect is due to omitted variable bias. We also use an alternative classificationof cause of death that is based on professional assessments of what deaths can be prevented and obtain very similar results.Finally, we examine the heterogeneity in the bereavement effect based on the time since the death of the spouse. For females,we find that the bereavement effect dissipates 24 months and more after the death of the spouse. In contrast, the effect formales is as strong 24 or more months after the death of the spouse as it is in the first six months. When we allow theseeffects to vary by cause of death, we again find evidence that the results for men are causal but the results for women aremost likely driven by an omitted variable bias.

2. Marriage, mortality, the bereavement effect, and data on marriage selection

2.1. Literature review

The antecedents for the current study flow from two different but related strands of literature. The first group of papersdocument lower mortality rates among the married. Empirical investigations of the differences in mortality rates between

2 If a spouse’s cause of death can be predicted by SES, it provides the researcher with information regarding the mortality of the surviving spouse; hence,we call this an informative cause of death. The opposing case is a cause of death that is not predicted by SES, thus we call this an uninformative cause ofdeath.

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married and unmarried individuals go back over a century to Farr (1858) and Durkheim (1897). The negative associationbetween marriage and mortality has been documented in the US by a number of authors including Gove (1973), Kobrinand Hendershot (1977), Smith and Waitzman (1994), Mergenhagen et al. (1985), Rogers (1995), Kisker and Goldman (1987),Lillard and Waite (1995), and Lillard and Panis (1996). This relationship has been established for other countries including 16developed countries (Hu and Goldman, 1990), England (Gardner and Oswald, 2004), Canada (Trovato, 1991), Israel (Manoret al., 2000), and Bangladesh (Rahman, 1993).

There are a variety of reasons why mortality rates may be lower among the married. Marriage may increase the financialstanding of the partners by increasing family income or providing insurance when bad health and/or financial shocks occur(Lillard and Waite, 1995; Waite and Gallagher, 2000). Marriage may also provide important psychological benefits such asreducing stress, improving one’s disposition or integrating a person into a community (Waite, 1995; Gove, 1973). A detailedliterature in epidemiology has established that those with greater social ties have better health and lower mortality (Berkmanand Syme, 1979; Blazer, 1982; House et al., 1982; Cohen et al., 1997). Finally, marriage may discourage risky behavior suchas smoking, heavy alcohol use or illicit drug use (Miller-Tutzauer et al., 1991; Curran et al., 1998; Duncan et al., 2006) orcriminal activity (Laub et al., 1998) or encourage healthy behavior such as visiting the doctor (Umberson, 1992; Verbrugge,1979).

In a related line of work, researchers have also documented heightened mortality of the recently widowed, a relationshipreferred to by some as the “bereavement effect”. This basic statistical relationship between widowhood and mortality hasbeen documented by a number of authors including Cox and Ford (1964), Parkes et al. (1969), Helsing and Szklo (1981),Kaprio et al. (1987), Mendes de Leon et al. (1993), Mineau et al. (2002), Korenman et al. (1997), and Lillard and Waite (1995),just to name a few. Excess mortality among the recently widowed has been demonstrated to exist in a wide variety of agegroups, socioeconomic levels, countries and cultures. The impact of a spouse’s death is qualitatively large. After controllingfor a variety of factors, Schaefer et al. (1995) and Kaprio et al. (1987) found that mortality rates double for the survivingspouse in the first year after the death of their spouse. Estimates also suggest that the bereavement effect is strongest in theperiod right after the death of a spouse (Lichtenstein et al., 1998; Manor and Eisenbach, 2003).

All of the studies mentioned above demonstrate excess mortality for surviving males, but the results for surviving femalesare less definitive. Helsing and Szklo (1981) found no excess mortality for widows, and Mineau et al. (2002) found smallereffects for widows compared with widowers, with the results for women varying considerably across birth cohorts. Lillardand Waite (1995) found some excess mortality for women, but the results were sensitive to model specification. Data oncouples from Northern California (Schaefer et al., 1995), Finland (Kaprio et al., 1987), and Israel (Manor and Eisenbach, 2003)found similar bereavement effects on mortality for males and females.

There are several pathways through which widowhood can become an immediate health risk. Some suggest that excessmortality is generated by the emotional stress of the death of a loved one (Martikainen and Valkonen, 1996; Luoma andPearson, 2002) or the emotional and physical stress of caring for the dying (Christakis and Iwashyna, 2003). Recent researchby Wittstein et al. (2005) suggests that emotional stress can cause the overproduction of particular hormones that cancause a sudden life-threatening heart spasm in otherwise healthy people. Rosenbloom and Whittington (1993) found elderlywidowed people suffer from poor nutrition right after the death of their spouse. The loss of a spouse may also reduce contactwith established social network, which, given in the literature cited above, may generate poorer health outcomes. Finally,Iwashyna and Christakis (2003) found evidence suggesting that widowhood compromises the quality of medical care soughtby the surviving spouse.

2.2. Behavioral correlations

The accumulated empirical evidence is convincing that mortality rates of the bereft are higher than their married counter-parts. Whether these events can be interpreted as causal relationships remains unclear. The results are potentially explainedby marriage selection which has no causal interpretation. There are strong positive correlations between many characteris-tics of married couples including age, years of education, IQ, height, waist circumference, and even earlobe length (Spuhler,1968; Vandenburg, 1972; Harrison et al., 1976; Mascie-Taylor and Gibson, 1979; Herbener, 1993; Caspi and Herbener, 1993;Murray, 2000). The similarity in the characteristics of spouses is also matched by a similarity in life events. Married couplesthat last past middle-age live through the same inter-temporal events, shocks, and income and consumption patterns. Sucha convergence of lives can explain why there is evidence that widowed spouses die soon after the loss of their spouse: simplyput, they started leading the same lives (Smith and Zick, 1994).

Not surprisingly, there are also strong correlations in the investments that husbands and wives make concerning theirhealth. Many married couples share a love of exercise, food, wine, cigarettes, or a sedentary lifestyle. In this section, wedocument this fact empirically with data for a sample of older married couples from the 1987 to 1990 National HealthInterview Survey (NHIS).3 The sample includes information on white, non-Hispanic married people aged 50–70.4

3 “The NHIS is the principal source of information on the health of the civilian non-institutionalized population of the United States and is one of the majordata collection programs of the National Center for Health Statistics (NCHS).” The survey contains data on roughly 60,000 households. More informationabout the survey is available at http://www.cdc.gov/nchs/about/major/nhis/hisdesc.htm (accessed March 25, 2008).

4 This sample roughly overlaps the time period and ages for the primary data set we use in later analyses.

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Table 1Conditional means of health behaviors, 1987–1990 NHIS and 1992/1993 CPS tobacco use supplement, white married males and females, 50–70 years of age

Variable Data set Married women

Pr(Xw = 1|Xh = 1) Pr(Xw = 1|Xh = 0) Difference

Obese? NHIS 0.233 (0.008) [2870] 0.124 (0.002) [17,426] 0.109 (0.007)Fair or poor health at survey? NHIS 0.450 (0.008) [3998] 0.097 (0.002) [16,298] 0.353 (0.006)Bed days in past 12 months? NHIS 0.500 (0.006) [6724] 0.275 (0.004) [13,572] 0.225 (0.007)Short-term hospital stay past 12 months? NHIS 0.118 (0.006) [2618] 0.091 (0.002) [17,678] 0.027 (0.006)Current smoker? CPS tobacco use supplements 0.401 (0.008) [3509] 0.123 (0.003) [15,316] 0.277 (0.007)

Married men

Pr(Xh = 1|Xw = 1) Pr(Xh = 1|Xw = 0) Difference

Obese? NHIS 0.258 (0.008) [3077] 0.133 (0.003) [19,094] 0.125 (0.007)Fair or poor health at survey? NHIS 0.507 (0.009) [3281] 0.117 (0.002) [18,890] 0.390 (0.007)Bed days in past 12 months? NHIS 0.482 (0.006) [8093] 0.255 (0.004) [14,078] 0.227 (0.006)Short-term hospital stay past 12 months? NHIS 0.143 (0.008) [1975] 0.114 (0.002) [20,196] 0.029 (0.008)Current smoker? CPS tobacco use supplements 0.459 (0.008) [4085] 0.147 (0.003) [17,433] 0.312 (0.007)

Table entries are fraction (standard error) [observations].

First, we consider whether knowing information about a husband’s health habits conveys any information about thewife’s health behavior. We look at four discrete outcomes: whether the person is obese (has body mass index > 30), whetherthey self-report fair or poor health, whether they had any bed rest days in the past 12 months, and whether they had ashort-term hospital stay in the past 12 months.5 We calculate the conditional probability that a wife (husband) answers yesto each of these questions (Xw = 1) given that their husband (wife) answers yes or no (Xh = 1 or 0).

The results from this exercise are reported in Table 1. Equality of the conditional probabilities means that the behaviorsand outcomes for wives and husbands are statistically independent. In the married women sample, for each of the fourvariables, the differences in the conditional probabilities are large, and we easily reject the null hypothesis that the conditionalprobabilities are equal. Wives with obese husbands are twice as likely to report they are obese. Wives with husbands in fairor poor health are 4.5 times as likely to report they are in poor health compared with when their husband are not in fair orpoor health.

In the lower half of the table, we repeat the exercise for males. In each of these cases, we can reject the null of equalityin the conditional means, and the relative differences and absolute differences in probabilities are similar to the sample ofmarried women.

The NHIS survey that we use in this analysis does not ask respondents whether they smoked. Supplemental surveys tothe NHIS do ask about smoking habits, but these surveys are typically only administered to one person in the household.Therefore, we cannot conduct this same analysis with this key health behavior. In the last row of each panel in Table 1, wegenerate probability estimates for whether a married respondent currently smoked based on whether their spouse smokesfrom the September 1992, January 1993 and May 1993 Tobacco Use Supplements from the Current Population Survey (CPS).6

Both married women and married men are about three times as likely to report they smoke when their spouse smokes,compared with when their spouse does not smoke.

3. Empirical methodology

Although there is convincing evidence that mortality is higher after the death of the spouse, the data in Table 1 does raisethe possibility that this result is simply an omitted variables bias. In this section, we outline our empirical methodologydesigned to help distinguish whether the bereavement effect is marriage protection or marriage selection. We begin with adescription of the data set used for this project.

3.1. Analysis sample and descriptive statistics

The primary data for this analysis are public-use versions of the National Longitudinal Mortality Study (NLMS). The data arethe product of a merging of person-level responses from the Census long-form data and the Current Population Survey (CPS)

5 Body mass index = 703 × weight (lb)/height2 (in2) and in the survey, height and weight are self-reported. On the questionnaire, self-reported healthstatus is ascertained by asking “Would you say [your] health in general is excellent, very good, good, fair, or poor?”; bed rest days is determined from “Duringthe past 12 months, about how many days did illness or injury keep [you] in bed more than half the day? (including days while an overnight patient)”; andshort-term hospitals stays is generated from a series of questions including “How many nights [were you] in the hospital?”.

6 The CPS is a monthly household survey of roughly 60,000 households designed to measure labor market conditions for the non-institutionalizedpopulation. Respondents are in the CPS for 4 months, out for 8, then back in the survey for 4 months. Therefore, the three smoking supplements representthree unique samples and are designed to be pooled together.

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to death certificate information from the National Death Index (NDI).7 We use a public-use version of the NLMS that containsdata from five monthly CPS samples from 1979 through 1981. The CPS data provides information on household income, laborforce status, individual education and other demographic variables; however, they do not provide any information on healthstatus or health behaviors at the time of the survey. The endpoint to the mortality follow-up is fixed to nine years fromentry into the CPS and the data indicates the days from the initial survey until death or the end of the follow-up, whichever comes first. Data from the NDI include information on the cause of death, which is recorded using the ICD-9 codingsystem.8 The NLMS contains CPS and NDI information for 637,162 individuals. The longitudinal component to this otherwisecross-sectional data set enables us to investigate how marital status impacts mortality.

We focus our attention on married, white, non-Hispanic people between the ages of 50 and 70.9 Using household iden-tification numbers and variables in the NLMS that indicate a respondent’s relationship to the head of household, we matchthe records of husbands and wives. Although spouses of 50–70 year olds are primarily within this age range, some are not, sothere are different sized samples for “married men” and “married women”. Our two NLMS samples consist of 37,777 marriedmen and 34,465 married women.

Table 2 provides the means for several of the key variables of interest from our analysis sample. Not surprisingly, a smallerproportion of women die within nine years of being surveyed (9 percent) than do married men (18 percent). Likewise, 8percent of married men become widowers after their initial interview, and 22 percent of married women lose their spouse.As a different exercise, we calculate mortality rates over a shorter period of time after the initial interview, and in Table 2,we also report the proportion of married men and married women that died within five years of entering the survey andthe proportion that were widowed over the same period. The 5-year mortality and widowhood rates are about one-half the9-year rates.

Table 2 also provides means and standard deviations for the income, education, occupation10 and age variables for theNLMS data. In public-use version of the NLMS, family income is reported in $5000 intervals through $25,000, then a groupfrom $25,000 to 50,000 and a final group with incomes in excess of $50,000.11 From more detailed education variables, weconstruct five dummy variables measuring education (no high school, some high school, high school graduate, some collegeeducation and a college graduate). We also construct 12 dummies for each 1-digit occupation code.

The average married woman is about 3 years older than the average married male. The median male and female belongs toa family that has between $20,000 and 25,000 in income. About 36 percent of males have less than a high school education andless than 17 percent are college graduates. The corresponding numbers for females are 32 and 9 percent, respectively. Amongmales that identify an occupation, craftsman is the mode, but for women, the majority report not working or occupation ismissing. Among working women, the most frequently reported occupation is clerical.

3.2. Baseline Cox proportional hazard models

In our sample, an observation consists of a married couple that enters the NLMS between 1979 and 1981. The observationperiod begins with this entry point and extends nine years, or until death, which ever comes first. The data are thereforeconsidered right-censored, because we do not observe events (i.e. widowhood and death) after the end of the mortalityfollow-up period. While there are several modeling techniques for the analysis of survival data, we follow previous work byemploying a Cox proportional hazard model, which is a partial maximum likelihood estimation method (Cox, 1972). The Coxmodel begins with the assumption that the hazard for individual i can be written as

hi(t) = �0(t) exp(Xiˇ), (1)

where for simplicity, we assume Xi is a vector of time invariant characteristics. The model assumes that the hazard at time tfor individual i is a function of the baseline hazard �0 (t), plus a function of observed characteristics. The baseline hazard isleft unspecified but it is assumed to be constant across people, meaning that the proportional hazard for person i relative toperson j for fixed time t is only a function of observed characteristics hi(t)/hj(t) = exp (Xiˇ)/exp (Xjˇ). To circumvent makingan assumption about the baseline hazard, the Cox model specifies a partial likelihood, which can be described as follows. Ifwe order the data from the shortest to longest spell t1, t2, . . ., tn, the conditional probability that person 1 dies at time period

7 For more information about the NLMS, please see Sorlie et al. (1995) and Rogot et al. (1992), and the NLMS web page http://www.census.gov/nlms/(accessed March 25, 2008).

8 ICD-9 is the International Statistical Classification of Diseases and Related Health Problems, 9th revision.9 We restrict our attention to whites because the statistical procedure outlined below to identify uninformative deaths did not identify any deaths

categories as uninformative for minorities. This is due to two features of our procedure. First, we need to guard against Type II errors which required thatwe re-aggregate many death categories into large groups. Coupled with the small samples for black and other minorities, we could not isolate small enoughdeath categories that could be used as uninformative deaths.

10 In the CPS, for persons who were employed at the time of the survey, the occupation variable relates to the job worked during the preceding week. Forunemployed persons and those not currently in the labor force were to give their most recent occupation.

11 During the time period we are considering, the family income variable from the basic monthly CPS was a 14-level categorical variable with incomesgreater than $75,000 being the top group. The public-use version of the data presents a less detailed version of family income to maintain confidentiality.

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Table 2Sample characteristics, white married males and females, 50–70 years of age, public-use NLMS

Variable Married males Married females

DiedWithin 9 years of survey 0.178 0.093Within 5 years of survey 0.091 0.044

Become widow/widowerWithin 9 years of survey 0.066 0.206Within 5 years of survey 0.032 0.112

Family income<$5K 0.041 0.052≥$5K, <$10K 0.132 0.166≥$10K, <$15K 0.169 0.186≥$15K, <$20K 0.142 0.138≥$20K, <$25K 0.154 0.143≥$25K, <$50K 0.285 0.248≥$50K 0.076 0.067

Education<High school 0.206 0.158Some HS 0.161 0.160HS graduate 0.343 0.463Some college 0.124 0.125College graduate 0.165 0.094

Age50–59 0.544 0.57260–70 0.456 0.428

OccupationHome maker <0.001 0.006Service 0.047 0.061Laborer 0.026 0.004Operaters 0.062 0.044Operate equipment 0.036 0.002Craftsmen 0.167 0.008Clerical 0.046 0.133Sales 0.047 0.035Managers 0.148 0.039Professionals 0.106 0.055Farming 0.052 0.014Missing/never worked 0.263 0.598

Individuals 37,777 34,465

Table entries are the sample fraction within each category.

t1, given that anyone could have died at that time, is

�0(t1) exp(X1ˇ)∑

i�0(t) exp(Xiˇ)= exp(X1ˇ)

∑iexp(Xiˇ)

. (2)

By definition, the baseline hazard drops out and the term on the right in Eq. (2) represents the partial likelihood forperson 1. The model is partial likelihood because the estimation does not exploit all the information in the data, namely, thebaseline hazard �0(t). As a result, the estimates for ˇ are consistent but not efficient. However, the benefit of the procedureis that the researcher does not have to specify the form for the baseline hazard �0(t). The Cox model outlined in (1) and (2)is easily adapted to include incomplete spells and time-varying covariates. In the study, we are primarily interested in a setof time-variant variables that indicate the period after respondent’s spouse has died.

Above, we raise the suspicion that unobserved or omitted variables are potentially biasing single-equation estimatesby illustrating the strong correlation in behavior between spouses using data not available in the NLMS. In an additionaleffort to support these concerns, we run a series of Cox proportional hazard models that begin with only the widowhoodvariable and progressively add more covariates. As we add more variables, if the estimated bereavement effect declines,this signals that widowhood is correlated with observed characteristics. Since we suspect, to some degree, that observedand unobserved characteristics are positively correlated, this would also indicate a concern that the bereavement effectsare capturing unobserved factors as well in the specifications without many covariates. The final results in this table willalso indicate a baseline specification to which we will compare our eventual models that allow for heterogeneity in thebereavement effect based on cause of death.

The results from these models are reported in Table 3. In specification 1, the only covariate is the time-varying indicatorfor when the spouse dies (widow) and we progressively add to the model four sets of time-invariant variables measured atbaselines: 4 indicators for level of education (specification 2), 6 indicators for family income (specification 3), indicators for

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Table 3Partial maximum likelihood estimates, Cox proportional hazard models, death during follow-up, white married males and females, 50–70 years of age,public-use NLMS

Model (1) Model (2) Model (3) Model (4) Model (5)

Married males, aged 50–70 (n = 37,777)Widow 1.787 (0.096) 1.702 (0.091) 1.542 (0.083) 1.439 (0.077) 1.316 (0.071)

IncludeEducation Yes Yes Yes YesIncome Yes Yes YesOccupation Yes YesAge Yes

Married females, aged 50–70 (n = 34,465)Widow 1.617 (0.078) 1.521 (0.074) 1.361 (0.067) 1.346 (0.066) 1.196 (0.059)

IncludeEducation Yes Yes Yes YesIncome Yes Yes YesOccupation Yes YesAge Yes

Table entries are hazard ratios (standard errors) from Cox proportional hazard models. There are up to 6 income, 4 education, 10 or 11 occupation, and 21age dummy variable included, depending on the specification.

occupation (specification 4), and 20 indicators for age (specification 5). There are two panels to Table 3—in the top panelare the Cox regression results for married men and in the bottom panel are the results for married women. Since all of thecovariates are dummy variables, we only report the hazard ratio. Of course, we expect the bereavement effect estimate tobegin to fall as more variables are introduced to explain the excess mortality of widows over people still married to theirspouses.

The results in Table 3 show for men and women that the magnitude of the bereavement effect drops by approximately 50percent as we move from the parsimonious to the fully specified model. For men, the hazard ratio begins at 1.787 and fallsto 1.316, and the fall is from 1.617 to 1.196 for women. The findings provide suggestive evidence that widowhood is stronglycorrelated with observed characteristics, and since we suspect correlation between observed and unobserved factors, theseresults provide suggestive evidence that marriage selection explains part of the temporal correlation in spousal mortality.

The results in the last column of Table 3 are comparable to other studies and provide the launching board for the nextsection. The point to take away is that after a wife dies the husband has a 32 percent greater risk of dying (hazard ratio(h.r.) = 1.32), and after a husband dies, a wife has a 20 percent greater hazard (h.r. = 1.20). Both of these results are statisticallydistinguishable from the null hypothesis that the h.r. = 1 at conventional levels.

3.3. Informative and uninformative causes of death

In an effort to isolate whether the bereavement effect estimated in Table 3 represents marriage selection or protection,we exploit the information contained in the heterogeneity in the bereavement across certain causes of death. If a cause ofdeath is democratic in its affliction, then the realization of the disease and the subsequent death of a spouse reveals lessinformation regarding the health of the surviving spouse; therefore, in these special cases, we are less concerned that thebereavement effect is driven by omitted variables that measure individual and couple behavior.

In what follows, we provide evidence that certain causes of death (COD) are uncorrelated with our measures of SES:income, education and occupation at the time of survey. This evidence leads to our claim that these COD are not explainedwell by the theory of assortative mating.

Our measures of SES are shared by the bulk of research that has examined the SES/mortality gradient for all-cause andcause-specific mortality (Berkman and Kawachi, 2000). The genesis for much of the work in social sciences is the research ofKitagawa and Hauser (1973) who matched survey data from the 1960 Census long-form, conducted in April of 1960, to deathrecords from the May–October 1960 period. The stylized facts from their work are that mortality rates decline with incomeand education but at a decreasing rate. This relationship is present for all age groups, but Kitagawa and Hauser find lessvariation in mortality across socioeconomic groups for the elderly, a result that has been replicated in more recent surveys(Hurd et al., 1999; Snyder and Evans, 2006).

With the NLMS data, we use detailed 3-digit ICD-9 cause of death information to construct a series of dummy variables toindicate whether a person died in the 9-year follow-up from a particular cause. For example, a dichotomous variable for thecause of death “ischemic heart disease” takes on the value of 1 for an individual who dies of ischemic heart disease. For bothmarried men and women, we then run a series of logistic regressions that identify whether the death from a particular causeis predicted by the income, occupation and education of the respondent—our SES measures, controlling for a cubic term inage. For each regression, we conduct four −2 log likelihood tests: whether the income dummies are jointly zero, whether theeducation dummies are jointly zero, whether the occupation dummies are jointly zero, and whether the income, educationand occupation dummies are jointly zero. If we can reject any of the four null hypotheses, then we consider the cause to be

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Table 4Uninformative causes of death (UCOD) for white married males and females, 50–70 years of age, public-use NLMS

Cause of death (first 3 digits of ICD-9) Number Proportion of UCOD (%)

MenPancreatic cancer (157) 107 9Other cancers (170–239, various)a 278 23Genital cancer (179–187) 212 18Lymphoma, leukemia (200–208) 203 17Cardiomyopathy (425) 65 6Pneumonia (480–487) 149 13Non-mv accidents, murder/suicide (800–807; 826–999) 174 14

Total # of deaths 1188% of all deaths 15.7% of sample 3.4

WomenOther cancers (140–239)b 301 30Breast cancer (174) 216 22Genitourinary cancer (179–189) 149 15General circulatory disease (390–459)c 241 24Accidents (800–999) 79 8

Total # of deaths 986% of all deaths 34.1% of sample 2.6

a These diseases include: neoplasms of bone, connective tissue and skin (ICD-9 codes 170–175); neoplasms of unspecified sites (190–199); benignneoplasms and carcinoma in situ (210–239).

b ICD 9 codes included are: 140–152;154–156; 157–161;163–173;175–178; 190–199.c These diseases include all general circulatory diseases except the following: acute myocardial infarction (410), other forms of chronic ischemic heart

disease (414), other forms of heart disease (420–429), intracerebral hemorrhage (431), other and unspecified intracranial hemorrhage (432), and occlusionof cerebral arteries (434).

an informative-COD group (ICOD). Likewise, if we cannot reject all four hypothesis tests, we consider the cause of death tobe uninformative (UCOD).

We are careful to not disaggregate death causes into too small of cells so that we have a high Type II error rate for the−2 log likelihood tests. To determine the minimum mortality rate that a death category must have, we first run logit modelsfor all 3-digit death categories. We then find the death category with the smallest mean where we can reject one of the fourtests outlined above.12 If a 3-digit death category falls below this minimum threshold, we aggregate it with other deathsfrom the same 2-digit category so the pooled deaths have a mean above the minimum threshold.13

In Table 4, we report the causes of death that fall into the uninformative categories for both men and women. The listincludes the number of deaths attributed to each cause, as well as each cause’s proportion of total UCOD deaths. We findthat 15 percent of deaths for men married to women aged 50–70 and 34 percent of deaths for women married to men aged50–70 fall into causes that are uncorrelated with observed characteristics.

We test the validity of our identification strategy using an analysis sample of women married to men aged 50–70 and menmarried to women aged 50–70 and extracted from the NLMS. For each sex, we run two logit models. In one specification,the dependent variable is the probability the individual dies of an UCOD within the sample time frame (the entire 9-yearfollow-up), and for the other specification, the dependent variable is the probability of dying of an ICOD under the sameperiod. The other explanatory variables consist of a full set of dummies for income, education, occupation and age groups.

The marginal effects from these logit models are listed in Table 5. We find an inverse, monotonic relationship betweenmortality and the SES variables for income and education when we model the probability of dying from an ICOD. Among theoccupation dummy variables, 5 of 10 are statistically significant at p < 0.05 in the male ICOD model and 2 of 11 are statisticallysignificant for women in the ICOD model. This is not the case for the group of UCOD. Here, none of the 21 coefficients inthe two UCOD models are statistically significant. The marginal effects we find in the UCOD models are all very small, andin every case but one (income less than $5000 in the male UCOD model), we cannot reject the null hypothesis that theindividual coefficient estimates are equal to zero.

The p-values for the various hypothesis tests are also listed in Table 5. For both men and women in the NLMS sample, weeasily reject the null that the ICODs are not correlated with income, education and occupation. All p-values for this outcomeare <0.0001. In contrast to the results for ICODs, the results for UCODs differ between men and women. For the wives of

12 For men married to women aged 50–70, malignant neoplasms of rectum, rectosigmoid junction, and anus is the 3-digit death category with theminimum mortality rate (37 deaths) and a p-value of 0.04 for the hypothesis test that all the education variables are equal to zero. For women married tomen aged 50–70, diabetes mellitus is the 3-digit death category with the minimum mortality rate (54 deaths) and a p-value of 0.05 for the hypothesis testthat all the income variables are equal to zero.

13 When we re-group into large categories, we use the ICD-9 72-category grouping as a guide.

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Table 5Maximum likelihood estimates of logistic regression, death from informative or uninformative causes in 9-years after initial interview white married malesand females, 50–70 years of age, public-use NLMS

Covariates Males Females

Observations: die within 9 years ofthe survey from an

Observations: die within 9 years ofthe survey from an

Informative death Uninformative death Informative death Uninformative death

Income <$5K 0.031 (0.006) 0.006 (0.003) 0.006 (0.002) −0.003 (0.002)$5K ≤ Income < $10K 0.025 (0.005) 0.002 (0.002) 0.004 (0.002) 0.002 (0.002)$10K ≤ Income < $15K 0.017 (0.004) 0.002 (0.002) 0.003 (0.001) 0.002 (0.002)$15K ≤ Income < $20K 0.011 (0.004) 0.002 (0.002) 0.002 (0.001) −0.001 (0.002)$20K ≤ Income < $25K 0.011 (0.004) 0.002 (0.002) 0.001 (0.001) 0.001 (0.002)$25K ≤ Income < $50K 0.006 (0.003) 0.001 (0.002) 0.001 (0.001) −0.001 (0.002)No high school 0.016 (0.003) −0.001 (0.001) 0.004 (0.002) 0.002 (0.002)Some high school 0.015 (0.003) −0.001 (0.001) 0.003 (0.001) 0.002 (0.002)High school graduate 0.008 (0.002) −0.001 (0.001) 0.002 (0.001) <0.001 (0.002)Some college 0.007 (0.003) 0.001 (0.001) 0.001 (0.001) <0.001 (0.002)Occupation: never work, missing value, etc. 0.025 (0.005) 0.003 (0.002) 0.009 (0.002) 0.001 (0.002)Farming −0.008 (0.003) −0.001 (0.002) −0.005 (0.002) −0.003 (0.004)Household NA NA 0.001 (0.004) −0.001 (0.005)Service 0.008 (0.004) 0.004 (0.003) 0.002 (0.002) < 0.001 (0.003)Laborers 0.002 (0.004) 0.004 (0.003) −0.002 (0.004) −0.001 (0.006)Operatives, not transport 0.004 (0.004) 0.001 (0.003) −0.002 (0.005) −0.002 (0.008)Operatives, equipment operative −0.002 (0.003) −0.001 (0.002) 0.003 (0.002) −0.002 (0.003)Craftsmen 0.002 (0.003) −0.001 (0.002) −0.001 (0.003) −0.007 (0.004)Clerical 0.011 (0.004) 0.001 (0.002) 0.002 (0.002) −0.001 (0.002)Sales 0.009 (0.004) −0.001 (0.002) 0.001 (0.002) −0.001 (0.003)Managers 0.005 (0.003) −0.001 (0.002) 0.002 (0.002) 0.001 (0.003)

p-Values on −2 log likelihood test statisticsEducation coefficients are all 0 <0.0001 0.542 0.005 0.502Income coefficients are all 0 <0.0001 0.168 <0.0001 0.071Occupation coefficients are 0 <0.0001 0.036 <0.0001 0.690Education, income and occupation coefficients are all 0 <0.0001 0.014 <0.0001 0.203

Mean of outcome 0.185 0.034 0.051 0.026−2 log likelihood 30,071.31 59,960.58 13,987.50 8,871.83

Table entries are marginal effects (standard errors) from a logistic regression. The reference person is someone married to a 50–70-year-old white non-Hispanic woman or man, and who is 50-year-old or younger, has a college degree, $50K or more in family income, and is/was employed in a professionaloccupation. Other covariates (not reported) include dummy variables for each age 51 through 70, plus a dummy for people 71 and greater in age.

men aged 50–70, we are able to support our assertion that income, occupation and education are uninformative becausethe p-value for the hypothesis test is 0.203. For the husbands of women aged 50–70, we are not able to reject the hypothesistest on the education parameters, p-value = 0.542, but we have weaker statistics for the other tests. While this suggests somecorrelation between SES and the probability of dying from an UCOD, the point estimates and marginal effects of the incomevariables are very small and close to negligible in comparison with the magnitudes of the point estimates and marginaleffects under the ICOD specification.

Another point of interest is whether a husband’s (wife’s) death from an UCOD or ICOD is correlated with the survivingwife’s (husband’s) type of death. If the probability of dying from an UCOD is significantly greater if the spouse died of anUCOD rather than of an ICOD, then we would argue that our classification system is incorrectly producing diseases that doreveal information regarding the mortality of the surviving spouse.

In Table 6 we investigate this issue by comparing the probability of a widow dying from an UCOD (ICOD) given the spousedied of an UCOD or an ICOD. Like Table 1, we compare the conditional probabilities by taking the difference of these twoprobabilities and check whether the difference is statistically different than zero. As the table shows, given that a spouse dies

Table 6Conditional means of death by type of cause, white married males and females, aged 50–70, public-use NLMS

Unconditional Conditional on

Spouse dies (1) Spouse died of UCOD (2) Spouse died of ICOD (3) |Difference| |(3) – (2)|Males

Pr[Die of UCOD by end of follow-up] 0.028 (<0.001) 0.028 (0.003) 0.030 (0.006) 0.027 (0.004) 0.003 (0.007)Pr[Die of ICOD by end of follow-up] 0.149 (0.002) 0.124 (0.007) 0.115 (0.011) 0.129 (0.008) 0.014 (0.014)

FemalesPr[Die of UCOD by end of follow-up] 0.031 (<0.001) 0.023 (0.002) 0.018 (0.004) 0.022 (0.002) 0.004 (0.005)Pr[Die of ICOD by end of follow-up] 0.062 (0.001) 0.054 (0.053) 0.044 (0.006) 0.057 (0.003) 0.014 (0.008)

Table entries are mean (standard error).

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of an UCOD or ICOD, we are unable to reject the hypothesis that the probability the surviving spouse dies from an UCOD isdifferent from the probability the surviving spouse dies of an ICOD.

4. Results

4.1. Bereavement effects for informative and uninformative deaths

In the last column of Table 3 we report the bereavement effect results from a Cox hazard model that includes as covariatesa complete set of fixed effects for age, income, education and occupation. Now we estimate two additional models where wereplace the time-variant widowhood variable with two time-variant variables that distinguish between types of widows:widow by UCOD or ICOD, and widow by unpreventable or preventable cause of death. The UCOD (ICOD) variable has a valueof 1 for the day, and each subsequent day, an individual becomes a widow by an UCOD (ICOD). In each of these models weinclude mutually exclusive set of age dummy variables plus we control for SES in these specifications by including time-invariant variables for income, education, age and occupation. We also test the null hypothesis that the bereavement effectfrom an ICOD (preventable COD) is equal to the effect from an UCOD (unpreventable COD).

The results for various Cox proportional hazard models are reported in Table 7. In the first two models, we present hazardratio estimates for men, and in the final two models, we report the estimates for women. We also report the standard errorfor the various covariates that measure widow/widower status.

Model (1) estimates are repeated from Model (5) of Table 3 and these numbers show that widowers have a 1.32 hazard ratioor widowers have 32 percent higher hazard of exiting life excess mortality compared to married men, and the bereavementeffects for widows are smaller at 20 percent. For both of these models, we can reject the null that the hazards equal one atconventional levels.

The second column in each group lists the Cox proportional hazard model results when we split the widowhood variableinto UCOD and ICOD. For men, the widowhood effect is nearly the same magnitude regardless of whether the spouse diesof an informative or uninformative cause of death. For both groups of death causes, we can reject the null that the hazardratios equal one and the p-value on the −2 log likelihood test that the coefficients are identical is very high (p-value = 0.79),so we cannot reject the null hypothesis that the two estimated bereavement effects are equivalent. The similarity in resultssuggests that the omitted variable bias is not large, and marital selection is not a major force in producing the observedbereavement effect for men. Thus, the loss of marital protection may indeed be the culprit in a widower’s demise.

For women in the NLMS, however, we find a different story. After breaking up the time-variant variable by cause of death,we find that widows of UCOD spouses have a bereavement effect (as measured by the hazard ratio) that is not statisticallydifferent from one. On the other hand, widows of ICOD spouses have a hazard ratio that is statistically distinguishable from1 (p-value < 0.001). One must be careful in interpreting these results. The substantial difference in the hazard ratios for ICODand UCOD deaths raises some suspicion of an omitted variable bias in the bereavement effect for women. However, thelarge standard errors on the hazard for the UCOD variable make it such that we cannot reject the null hypothesis that theICOD/UCOD hazard ratios are the same (p-value = 0.22). These results are suggestive of an omitted variables bias but notdefinitive.

The ability to differentiate between causation and correlation based on the results in Table 7 is a function of our ability toisolate those causes that are essentially random in the population. While we have followed a procedure to isolate causes ofdeath that are uncorrelated with SES characteristics, there is still some chance that the list of diseases in the UCOD categoryare somehow reflective of the surviving spouse. This is a much bigger concern for the married males sample because the likelyoutcome of including informative causes of death in the UCOD group would be to drive that coefficient closer to the ICODvalue. The lack of any noticeable bereavement effect for UCOD in the married females sample is reassuring. In contrast, somecauses of death grouped into the UCOD category are potentially ICODs in the sense that anecdotal evidence and researchpoint to individual behavior as an important component in explaining the likelihood of death. For example, “sun-tanning” isa behavior which raises the chances of developing skin cancer (Holly et al., 1995; Kricker et al., 1991). Researchers have foundthat cigarette smoking is a risk factor for pneumonia (LaCroix et al., 1989), acute myocardial infarction (Croft and Hannaford,

Table 7Partial maximum likelihood estimates, Cox proportional hazard models, death during follow-up, white married males and females, 50–70 years of age,public-use NLMS

Covariate Married males Married females

Model (1) Model (2) Model (1) Model (2)

Widower 1.316 (0.071) 1.196 (0.059)Widower due to uninformative-COD 1.360 (0.121) 1.041 (0.129)Widower due to informative-COD 1.293 (0.085) 1.216 (0.063)

−2 log likelihood 129,943.05 129,942.84 63,773.35 63,771.79p-Value, −2 log likelihood test 0.647 0.212

Table entries are hazard ratios (standard errors) from Cox proportional hazard models. The −2 log likelihood tests test for the equality of the coefficients inthe ICOD and UCOD models. Other covariates (not reported) include a complete set of dummy variables for income, education, occupation and age.

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1989; Wilhelmsen et al., 1984), and cancer of several types including pancreas (Tai et al., 2007), lip and oral cavity (Macfarlaneet al., 1995), nasal cavity (Brinton et al., 1984), pharynx and larynx (Franceschi et al., 1990), bladder (Taylor et al., 1998), andstomach (Brown and Devesa, 2002). Alcohol is a risk factor for all types of accidents (Thun et al., 1997), cardiomyopathy(Klatsky et al., 1990; Afonso et al., 2007), acute myocardial infarction, and cancers of the stomach, esophagus, small intestine,and duodenum (Brown and Devesa, 2002; Hansson et al., 1994). Obesity has been linked to acute myorcardial infarction(Yusuf et al., 2005), uterine cancer (Austin et al., 1991), kidney cancer (Key et al., 2002), and breast cancer (Morimoto et al.,2002; van den Brandt et al., 2000), as well as several other diseases already listed. Some of the causes of death groupedinto the UCOD category, though, are not rooted in individual behavior. In these cases, genetics, radiation, or other individualmorbidity are more often cited as the risk factors (Fentiman et al., 2006; Velicer et al., 2006; Smith et al., 2001, 2003; Adamiet al., 1998).

In theory, we could define UCOD as deaths that are uncorrelated with SES characteristics and behaviors. However, thepublic-use NLMS does not have any control variables that measure health status or health behavior. Therefore, we cannotproduce a more refined group of UCOD diseases. We can however, test the sensitivity of the hazard ratios to changes in theset of UCOD. Using similar duration models for both men and women and given the full set of UCOD as before, we take onecause of death category out of the UCOD grouping and place it in the ICOD grouping. We then re-estimate the basic modelfrom Model (2) of Table 7. Following this, we return the cause of death to the UCOD grouping, select another cause of death totransfer from the UCOD to ICOD group and follow the same procedure as above. We do this for each cause of death categoryin the UCOD groupings for men and women.

The results of this exercise provide a distribution of hazard ratios for men and women. For widowers, the estimated hazardratios range from 1.30 to 1.43 depending on which cause of death is removed from the set of UCOD. For each specification, wecannot reject the null hypothesis that the UCOD and ICOD hazard ratios are equal which supports our finding of a bereavementeffect among men. The distribution of hazard ratios is narrow and centered about the original UCOD estimate (1.36).

For widows, the story is slightly different as the UCOD hazard ratios are more dispersed, ranging from 0.87 to 1.16.We cannot reject the null hypothesis that the hazard ratios for ICOD (1.22) and UCOD (1.04) are equal under the originalspecification (p-value = 0.218). However, when we remove the “other accidents” category from the UCOD grouping, we findstronger evidence for a significant difference in the estimates (p-value = 0.104) and more evidence to suggest that women donot experience a bereavement effect. We also find for widows that when pneumonia is removed from the UCOD grouping,the hazard ratio jumps to 1.16 which is very close to the ICOD estimate (h.r. = 1.20). Lastly, ignoring the two outliers (h.r. = 0.87and 1.16), the distribution narrows to hazard ratios ranging from 0.94 to 1.06.

4.2. An alternative classification: preventable and unpreventable causes of death

The method we use to identify UCOD is a statistical exercise and does not rely on epidemiological research; therefore,we borrow from this line of literature to develop an additional layer of analysis that parallels the models above. The resultsof this exercise provide us a method to verify the results of the UCOD/ICOD specifications. Generally, causes of death varyfor many reasons, but one important dimension by which they differ is in their preventability. For example, liver cirrhosisis often the result of alcohol abuse, and because there are means to alter this behavior, the disease can be consideredpreventable. On the other hand, the causes of multiple sclerosis are to date largely unknown; thus, this disease can beconsidered unpreventable.

Phelan et al. (2004) developed a preventability scoring index for causes of death that ranges from 1.0 for a cause that isalmost entirely unpreventable (e.g., gall bladder cancer) to 5.0 for a cause that is almost entirely preventable (e.g., accidentalpoisoning). Two of the authors, both of whom are physicians and epidemiologists, independently rated the causes of death“in terms of the degree to which death was amenable to prevention or delay during the 1980s in the United States” (p. 272).Prevention can be due to either intervention by the person (abstaining from heavy drinking) or by the medical communityvia timely diagnosis and treatment. Using the preventability scoring, we develop a set of causes of death that cannot beexplained by individual tastes for preventative behavior. For our purposes, the set of unpreventable causes are those diseaseswith a score of 2.0 or lower according to the preventability scoring index.14,15

In Table 8, we list the unpreventable diseases from Phelan et al., the ICD-9 code, and the number of deaths over the9-year follow-up in both the white married male and female subsamples. The causes of death listed in the table that are inbold-faced type are those that appear as uninformative deaths in either the male or female samples listed above. There aresome notable overlaps between the two lists but in general, most of the death categories that Phelan et al. list as preventableare infrequent events, and based on our grouping procedure to prevent Type II errors outlined above, we would not haverun individual logit models to determine informative/uninformative status for these particular causes. Note also that the

14 The preventability index in Phelan et al. is based on deaths in the entire population. In comparison, our sample of interest is married whites aged 50–70.The list in Phelan et al. may be larger or smaller if one considers this more restrictive group.

15 We conduct supplementary analysis and allow the constraint on the preventability score to vary. We only consider expansions of the group of preventablecauses: diseases with (1) scores at or below 2.5 and (2) scores at or below 3.0. The hazard ratio for UCOD widowers remains stable as the preventabilityconstraint is relaxed, however, the hazard ratio for UCOD widows increases from 1.05 (preventability score (p.s.) ≤ 2.0) to 1.20 and 1.26 (p.s. ≤ 2.5 and 3.0,respectively), which is what we would expect if we start to add more suspect causes into the UCOD group.

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Table 8Preventable and unpreventable causes of death from Phelan et al. (2004), and frequency of events in white married males and females, 50–70 years of age,public-use NLMS

Disease (ICD-9 code) # of deaths in sample (married whites, aged 50–70)

Males Females

Malignant neoplasm of gallbladder/extrhepatic bile ducts (156) 13 8Multiple sclerosis (340) 3 10Anterior horn cell disease (335) 17 7Cardiomyopathy (425) 65 20Disorder of lipid plasma protein metabolism (272) 2 4Leukemia of unspecified cell type (208) 20 12Lymphosarcoma and reticulosarcoma, (200) 17 8Malignant neoplasm of brain (191) 51 33Malignant neoplasm of ovary and other uterine adnexa (183) 0 67Malignant neoplasm of if pancreas (157) 107 60Multiple myeloma and immunoproliferative neoplasms (203) 33 27Myeloid leukemia (205) 39 21Myoneural disorders (358) 2 0Muscular dystrophies and other myopathies (359) 3 2Polyartheritis nodosa and allied conditions (446) 1 1

Total number of deaths 373 280% of all deaths 4.9 9.7% of sample 1.1 0.74

unpreventable causes of death are decidedly less frequent than uninformative cases of death, with only 1 percent of malesand 0.74 percent of females dying from these causes.

Preventability is close in spirit to the idea of an informative cause of death in that a preventable cause of death likelyprovides information regarding the mortality of the surviving spouse. Alternatively, an unpreventable cause of death wouldnot reveal information regarding the mortality of the surviving spouse because of its nature. As a check to this supposition,we estimate models similar to those in Table 5. Specifically, for males and females, we estimate two logit models. In thefirst, the outcome of interest is an indicator that equals one if the respondent died during the nine years of follow-up froma preventable cause of death. In the second, the outcome variable equals one if the respondent died from an unpreventablecause. In these models, we include full sets of dummy variables for age, education, income and occupation. The marginaleffects for income and education are reported in Table 9 and to conserve space, we suppress the reporting for the age andoccupation variables.

As in Table 5, the marginal effects in both the male and female preventable death logits show a pronounced income andeducation gradient. The p-values for the tests that the income, education, occupation are all zero and incredibly small. Incontrast, none of the income, education or occupation marginal effects are statistically significant in the logits for death

Table 9Maximum likelihood estimates of logistic regression, death from preventable or unpreventable causes in 9-years after initial interview white married malesand females, aged 50–70, public-use NLMS

Males FemalesDied by the end of the follow-up from an Die by the end of the follow-up from an

Preventable death Unpreventable death Preventable death Unpreventable death

Income < $5K 0.0361 (0.0066) 0.0021 (0.0017) 0.0051 (0.0027) 0.0011 (0.0013)$5K ≤ Income < $10K 0.0275 (0.0051) 0.0009 (0.0010) 0.0066 (0.0023) 0.0005 (0.0009)$10K ≤ Income < $15K 0.0188 (0.0043) 0.0009 (0.001) 0.0045 (0.0021) 0.0009 (0.0010)$15K ≤ Income < $20K 0.0122 (0.0039) 0.0012 (0.0011) 0.0016 (0.0019) 0.0002 (0.0009)$20K ≤ Income < $25K 0.0126 (0.0039) 0.0007 (0.0008) 0.0010 (0.0019) 0.0016 (0.0011)$25K ≤ Income < $50K 0.0058 (0.0033) −0.0004 (0.0005) −0.0006 (0.0017) 0.0012 (0.0009)No high school 0.0164 (0.0036) −0.0004 (0.0005) 0.0064 (0.0023) 0.0010 (0.0010)Some high school 0.0156 (0.0036) −0.0004 (0.0005) 0.0044 (0.0021) 0.0007 (0.0009)High school graduate 0.0080 (0.0026) −0.0003 (0.0005) 0.0027 (0.0017) 0.0000 (0.0006)Some college 0.0079 (0.0030) −0.0005 (0.0006) 0.0018 (0.0018) −0.0001 (0.0007)

p-Values on −2 log likelihood test statisticsEducation coefficients are 0 <0.0001 0.616 0.005 0.465Income coefficients are all 0 <0.0001 0.362 <0.0001 0.279Occupation coefficients are all 0 <0.0001 0.636 0.0059 0.799Education, income and occupation coefficients are all 0 <0.0001 0.709 <0.0001 0.650

Mean of outcome 0.185 0.034 0.051 0.026

Table entries are marginal effects (standard errors) from a logistic regression. Other covariates include dummy variables for each age 51 through 70 and adummy for ages 71 and over. The reference person is someone married to a 50–70-year-old white non-Hispanic woman or man, and who is 50 years old oryounger, has a college degree, $50K or more in family income, and is/was employed in a professional occupation.

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Table 10Partial maximum likelihood estimates, Cox proportional hazard models, death during follow-up, white married males and females, aged 50–70, public-useNLMS

Covariate Married males Married females

Model (1) Model (2) Model (3) Model (1) Model (2) Model (3)

Widower 1.316 (0.071) 1.196 (0.059)Widower due to unpreventable COD 1.377 (0.237) 1.058 (0.232)Widower due to preventable COD 1.310 (0.074) 1.202 (0.060)Widow due to either uninformative or unpreventable COD 1.311 (0.114) 1.064 (0.128)Widow due to other cause of death 1.318 (0.088) 1.219 (0.063)

−2 log likelihood 129,943.1 129,943.0 129,943.1 63,773.4 63,773.0 63,772.1p-Value, −2 log likelihood test 0.777 0.956 0.560 0.281

Table entries are hazard ratios (standard errors) from Cox proportional hazard models. The −2 log likelihood tests test for the equality of the preventableand unpreventable CODs in Model (2), or the equality of the coefficients on uninformative or unpreventable and other causes in Model (3). Other covariatesinclude a complete set of dummy variables for income, education, occupation and age.

by an unpreventable cause of death. At the bottom of the table, the p-values for the joint tests that the income, education,occupation and all three sets are jointly zero are all very high. Much like uninformative causes of death, unpreventable causesof death should provide little information about the surviving spouse. As in Table 7, we estimate Cox proportional hazardmodels for both sexes and allow the bereavement effect to vary between preventable and unpreventable causes of death.For the purpose of verification, the results from these specifications should produce similar inferences to the earlier results,even though the set of causes of death differ.

In Table 10, we report estimates of the bereavement effect where the coefficients are allowed to vary by preventabilityof the spouse’s death (Model 2). The results for this analysis tell a very similar story to the estimates for informa-tive/uninformative causes. For men, the hazard ratio for the widowers of spouses who die of unpreventable causes of death(h.r. = 1.377) is not statistically different than the ratio for the widowers of spouses who die of more preventable causes(h.r. = 1.377) and both hazards are statistically distinguishable from 1. For women, we find suggestive evidence of a selectionbias in that the hazard ratios for spouse’s deaths by a preventable cause are large and statistically different from 1, but thehazard for a spouse’s unpreventable death is small. Like the previous column, however, we cannot reject the null hypoth-esis that the two hazard ratios are equal. Not surprisingly, given the smaller number of unpreventable deaths compared touninformative deaths, the standard error on the hazard for the spouse’s death from an unpreventable cause has doubledcompared to the similar estimate from column (2).

In an attempt to reduce the standard error on the cause of death that provides little information about the surviving spouse,in Model (3) of Table 10, we allow the bereavement effect to vary based on whether the deaths are either uninformative orunpreventable, versus all other causes of death. The results from this exercise are identical to the results from the previousmodels: the bereavement effect for males is the same regardless of the cause of death but for women, the uninformativecauses of death show little bereavement effect but large standard errors.

4.3. Does the bereavement effect decline over time?

A number of authors have examined whether the bereavement effect varies with the length of time since the death ofa spouse and most of the evidence suggests that mortality is greatest right after the death of a spouse (Lichtenstein et al.,1998; Manor and Eisenbach, 2003). After controlling for a variety of factors, Schaefer et al. (1995) and Kaprio et al. (1987), forexample, found mortality rates double for the surviving spouse in the first year after the death of their spouse. The evidencedoes however show some heterogeneity across samples. Johnson et al. (1976) found higher mortality rates for widowedmales and females, but the impact drops off sharply as the time since widowhood increases for females. In contrast, theauthors show a smaller dropout in the impact of bereavement on mortality for widowed males.

In this section, we examine this same question with our analysis samples allowing for two alterations to the basic model.First, we generate a baseline specification where we reproduce some of the models from the previous literature and allow thebereavement effect to vary based on the time since the death of the spouse (Model 1). In this case, we consider bereavementeffects that are within 6 months of the death of the spouse, 6–24 months, and greater than 24 months. Next, we allow thesethree estimates to vary based on whether the death was an uninformative or informative cause of death (Model 2).

The hazard ratios from these models are reported in Table 11. In Model (1), we reproduce some of the results from theliterature. For males, the bereavement effect does not dissipate as we lengthen the time from the death of the spouse. In allcases for males, the hazard ratio is roughly 1.30 and for the coefficients that are between 6 and 24 months and greater than24 months, we can easily reject the null at conventional levels that the hazard ratio is 1. The estimated bereavement effectfor males are so close that the hazard ratio for males is within one one-hundredth of a point for deaths within 6 months anddeaths greater than 24 months. The p-value that the coefficients are the same is 0.92.

The estimates for Model (1) for women tell a different story. The bereavement effect declines monotonically as we lengthenwindow of observations after the death of the spouse. The hazard ratios for the three time periods are 1.40, 1.31, and 1.13,respectively. The first two are statistically distinguishable from 1 at the 0.05 p-value and the last is at the 0.10 p-value. But,

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Table 11Partial maximum likelihood estimates of Cox proportional hazard model, death during follow-up, white married males and females, aged 50–70, public-useNLMS

Covariate number Covariate Males Females

Model (1) Model (2) Model (1) Model (2)

(1) Spouse died <6 months ago 1.327 (0.197) 1.404 (0.177)(2) Uninformative death 1.399 (0.350) 1.092 (0.387)(3) Informative death 1.291 (0.236) 1.463 (0.196)

(4) Spouse died 6–24 months ago 1.275 (0.121) 1.265 (0.104)(5) Uninformative death 1.454 (0.223) 1.029 (0.231)(6) Informative death 1.185 (0.143) 1.308 (0.114)

(7) Spouse died >24 months ago 1.335 (0.093) 1.127 (0.070)(8) Uninformative death 1.301 (0.156) 1.033 (0.166)(9) Informative death 1.353 (0.114) 1.141 (0.075)

−2 log likelihood 129,942.89 129,941.65 63,770.16 63,768.10

p-Value on −2 log likelihood tests(1) = (4) = (7) 0.922 0.195(2) = (3) 0.796 0.438(5) = (6) 0.291 0.315(8) = (9) 0.786 0.558(2) = (3) and (5) = (6) and (8) = (9) 0.740 0.582

Table entries are hazard ratios (standard errors) from Cox proportional hazard models. Other covariates include dummy variables for each age 51 through70, plus a complete set of dummies for income, education and occupation.

given the standard errors on estimates, the p-value on the test that the coefficients are the same is almost 0.20. So in general,the bereavement effect for women dissipates considerably for women but not for men.

When we allow the bereavement effect to vary both by time since the death of the spouse and cause of death, wereproduce the results from our previous analyses. In Model (2) in Table 11, we see for widowed males, that there is noqualitative difference in the bereavement effect based on the cause of death of their spouse either within 6 months or after24 months of the death of their spouse. There is a noticeable difference in the hazard ratios for informative and uninformativedeaths within 6–24 months but as with all cases, these differences are not statistically significant. For males, the bereavementeffect hazard ratio for uninformative deaths within 6–24 months is statistically different from 1 at the p = 0.05 level and thesame coefficient for 24 and more months is statistically significant at the p = 0.10 level. In no case can we reject the null thatthe coefficients for uninformative and informative deaths are the same.

For women, Model (2) shows qualitatively small hazard ratios for all uninformative deaths. The standard errors on theseestimates are however so large that we cannot reject the null that the hazard ratios for uninformative and informative deathswithin time intervals are equal. As with the previous models, the results for males are convincing, the results for women aresuggestive.

5. Conclusion

Although a number of papers have established a heightened mortality for the survivor after the death of the spouse, thesimilarities in lifestyles, age, experience, and behaviors between a married couple call into question whether this result isindicative of the protective effects of marriage or whether the result is simply marriage selection. For males, the death of theirspouse from informative causes of death reveals a lot of information about their SES so we learn little about the causal effectof bereavement on mortality by looking at mortality patterns after a spousal death from one of those causes. In contrast, thefact that the bereavement effect is as large for surviving husbands when their wives die from uninformative causes, that is,causes of death that reveal little about the survivor, suggests the bereavement effect is causal.

Our results for women are less clear cut. The bereavement effect for surviving wives when their husband dies of anuninformative cause is small but with a large standard error, making it statistically indistinguishable from the effect forinformative causes.

There are a number of caveats to our work. The analysis only considers one measure of the health benefits of marriage(lower mortality) and the paper addresses an indirect measure of the health benefits of marriage (the rapid demise in healthfor some after the death of a spouse). That said, we have made progress analyzing this particular and well-studied aspect ofthe marriage/health literature. Second, death is our only longitudinal variable, so we do not observe some transitions thatmay contaminate the work. For example, a couple that divorces or separates after the survey date would be classified asmarried in our analysis. A more detailed longitudinal data set like the Panel Study of Income Dynamics would provide alonger list of time-varying covariates but the sample size drop would make the exercise useless. Given the sample sizes forcurrent longitudinal data sets, adding more covariates does not seem like a viable strategy. Larger sample sizes in a mortalitysample would however allow us to use finer breakdowns in causes of death when identifying uninformative causes of death.This could potentially generate greater agreement between the uninformative and unpreventable causes of death. Finally, it

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would be useful to have list of unpreventable diseases for those 50–70 instead of the current metric that focuses on deathsacross all age groups.

As with most papers, our results raise more questions than they answer. The most compelling being why for uninformativecauses of death is there a large bereavement effect for surviving males and a lack of an effect for women? Some possiblehypotheses cannot explain the disparity in results. We do not believe the results for women are simply a Type II error. Fewermen outlive their wives and we were able to find a bereavement impact on men so the lack of results for women is most likelynot due to a lack of power. More importantly, there are fewer uninformative deaths among women making the results for meneven more dramatic. Some papers in this literature suggest that among the elderly, living alone may increase mortality butour calculations from the 1980 Census indicate there is no difference in the fraction living alone among widows or widowers,aged 50–70 (roughly 59 percent for both groups). Likewise, there is some evidence that the bereavement effect is larger forpeople of younger ages but we find little difference in our sample for the average age when husbands and wives lose theirspouse (65.6 years for widows, 66.4 for widowers).

Previous literature points to a number of possible explanations for the disparity in results between men and women. Aswe outlined above, many older men rely heavily on their spouses for activities that are key for health such as schedulingdoctor visits, reminding them about taking their medicine, cooking, etc. In this situation, males would suffer more from theloss of spouse than married women. Likewise, women may have deeper social networks than men to help shield them fromthe psychological costs of bereavement. There is some evidence that the impact of widowhood on the incidence of depressionis greater for men than women (Lee et al., 2001) although the results do not always show a gender difference (Feinson, 1986).Most women also may expect to outlive their husbands so the psychological shock to them of the death of as spouse may notbe as dramatic. Working against these explanations is however the fact widowers appear to make some adjustments thatshield them from the stress of widowhood. For example, Helsing et al. (1981) estimate that remarriage reduces the chanceof death for widowers but not widows, and older widowers are more likely to remarry than elderly widows (Smith et al.,1991).

Although both the marriage protection and marriage selection hypotheses explain the observed patterns in the data,only the former purports a causal relationship between marriage and mortality. Deciphering which story is correct can haveinteresting policy implications. Standard cost-effectiveness studies produce an estimate of the cost of treatment per qualityadjusted life year saved. The denominator in this value is exclusively the patient being treated. However, if widows die atmuch higher rates in the first year after the death of the husband and this event can be attributed to marriage protection,standard cost-effectiveness estimates may understate the benefits of certain treatments (Christakis, 2004).

Acknowledgements

The authors wish to thank Seth Sanders, John Wallis, Suzanne Bianchi, Robert Kaestner, Jon Skinner and Nicholas Christakisfor a number of helpful comments. This research was supported in part by a grant from the Russell Sage Foundation.

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