Media, intention and final vote:

A two-wave panel data study to the effects of media factors on the PvdA and VVD vote

Two-wave panel data

Assignment 8

Mark Boukes (markboukes@Hotmail.com)5616298

1st semester 2010/2011Dynamic Data Analysis

Lecturer: Dr. R. VliegenthartJanuary 28, 2010

Communication Science (Research MSc) Faculty of Social and Behavioural Sciences

University of Amsterdam

Table of contents

INTRODUCTION AND THEORY.......................................................................................................................1

METHOD.................................................................................................................................................................2

RESULTS.................................................................................................................................................................4

MAXIMUM LIKELIHOOD ESTIMATION WITH BINARY LOGISTIC REGRESSION.........................................................4

CONCLUSION........................................................................................................................................................6

REFERENCE..........................................................................................................................................................7

APPENDIX A: TELEVISION PROGRAMS USED FOR THE INDEPENDENT VARIABLES

Appendix B: Do File

Media, intention and final vote:A two-wave panel data study to the effects of media factors on the PvdA and VVD vote

Mark Boukes

Introduction and theoryIn this study, I aim to investigate 1) certain assumptions that are often made by politicians but

also communication scholars and 2) a more investigated and well-known theory. First, I will

test whether certain media really have the political influence that is assumed by some people.

It is frequently said that programs of public broadcasters belong to the ‘left church’ and that

De Volkskrant is a left newspaper, whereas De Telegraaf is a newspaper with right-wing

sympathies; Algemeen Dagblad, NRC Handelsblad and the commercial broadcasters seem to

have a less obvious political stance. This study investigates whether these media indeed have

the effect on their viewers and readers as often is assumed. In the period before elections an

increase in media attention for this democratic process is logically expected; therefore, it is

also reasonable to expect potential effects to take place in that period. Furthermore, the well-

known bandwagon-effect (McAllister & Studlar, 1991) will be tested; are voters who expect

that a party will win many seats in Parliament more likely to vote for that party, than voters

who expect a less good result?

I will focus on (potential) voters of two parties: the PvdA (socialists) and VVD

(liberals). The decision to choose these two parties is based on poll and election results (see

also Figure 1) and the characteristics of the parties. First, the PvdA is a left-wing party,

whereas the VVD is a right-wing party, which makes it interesting to compare the effects on

both parties. Furthermore, the PvdA lost many seats in the last weeks before the elections

according to the poll results the Politieke Barometer of Interview-NSS (now Synovate), what

makes it interesting to find potential causes of the losses.

Consequently, four hypotheses will be tested focusing on the effects of television,

newspapers and expectations.

H1: Viewers of public broadcasting programs will be more likely to change their

political preference in a left political direction in the period before the elections and

therefore are more likely to vote for the PvdA at the time of the elections, whereas

they are less likely to vote for the VVD, compared to a first measure of vote intention

some weeks before the elections.

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H2: Readers of De Telegraaf will be more likely to vote for the VVD at the time of the

elections, whereas they are less likely to vote for the PvdA, compared to a first

measure of vote intention some weeks before the elections.

H3: Readers of De Volkskrant will be more likely to vote for the PvdA at the time of

the elections, whereas they are less likely to vote for the VVD, compared to a first

measure of vote intention some weeks before the elections.

H4: People, who estimate the number of seats a political party will win in the elections

higher, will be more likely to vote for that party, than those who estimate this number

lower, compared to a first measure of vote intention some weeks before the elections.

Figure 1. Poll results of the weeks before the 2006 Dutch Parliamentary election and the election results

MethodTo investigate the hypothesis a two-wave panel survey was used, the ‘Dutch Parliamentary

Election Studies 2006’1. Statistics Netherlands (CBS) carried out the fieldwork; interviews

were conducted face-to-face or by telephone; via a self-completion questionnaire the second

part of the questions were posed. A two-stage procedure was followed to find the sample of

respondents: first, municipalities were selected with unequal chances to the number of persons

in the municipalities; second, persons living in the selected municipalities had an equal

chance to be invited to participate in the survey. The total non-response rate of the survey was

51.7 percent. The survey was rather representative for the Dutch population, though people

1 http://www.dpes.nl/pages/nko_2006.php

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with a non-Western origin were underrepresented. The dataset contained the answers of

almost 2000 respondents (N = 1,895).

The dependent variable in this study is measured in the second wave by the question

‘Which party did you vote for at the elections of 22 November?’ and the lagged dependent

variable was measured in the first wave by the question ‘Which party will you vote for at the

elections of 22 November?’ (with a do-not-know-yet possibility). Dummy variables were

created for either having voted on the PvdA, having voted on the VVD (both wave 2), having

had the intention to vote for the PvdA, and having had the intention to vote for the VVD (both

wave 1).

In an original way, via an additive score for the variables indicating how often

particular programs are watched (1-5 scale, never – almost daily), the two independent

variables were created to measure how often respondents watch public broadcasting television

or commercial television. For both variables, the same number of programs were chosen

which are highly similar; for example, when a talk show was chosen for commercial

broadcasters also a similar talk show was chosen for the public broadcaster; the news on the

Dutch public broadcaster NOS was included, so the news on commercial broadcaster RTL4

was also included, etc. In total, for both independent variables (‘watching public

broadcasting’ and ‘watching commercial broadcasting’) eight similar programs were selected

(see Appendix A for the programs).

Furthermore, variables were already present in the dataset for if the people read certain

newspapers; those just needed to be recoded into dummy variables. To investigate the presence

of a bandwagon-effect, the variables were used that were obtained by the question ‘How many

seats do you think [party] will get in the next elections?’. Because some respondents answered

with numbers that were obviously not credible (lower than 10 or more than 40 for the VVD /

lower than 10 or more than 60 for the PvdA), those were set to missing, just as was the case for

the respondents who did not answer this question.

Next to this, control variables were created or changed for the analysis. Age was

calculated by subtracting the year of birth from 2006. Gender was measured by a dummy for

being male. Dummy variables were also created for education; respondents either completed

low level education, middle level education or high level education. The household income

was already measured in a useable way. A dummy was created for being religious.

To analyse the effects of the different media on the real vote of respondents a logistic

regression analyses was conducted using Stata 10.1. The analysis controlled for the lagged

dependent variable, which is the intention to vote or not for a certain party some weeks before

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(in wave 1). A logistic regression was necessary to investigate the effect on the odds of

respondents having voted for one party (score 1) or not (score 0). An inspection of the outliers

of this model showed that some respondents stand out with high standardized residuals,

however these cases seem to represent natural deviations, not miscoded observations or wrong

interpretations and are therefore kept in the sample; except, as specified above, for those with

strange estimates for the number of seats a party would gain.

ResultsBefore the results of the logistic analysis are presented, first an overview will be presented so

it is clear how much the real votes vary from the intentions people had to vote. Table 1 shows

the number of voters who did and who did not change their vote compared to their intention to

vote for one of the parties. It becomes clear that of only about 10 percent of the voters the real

vote differs from the intended vote. Via the logistic regression analysis it was investigated

which media factors could have caused these differences.

Table 1. Variation between vote intention and real vote

  Intention to vote PvdA   Intention to vote VVD  No Yes   No Yes

Vot

ed P

vdA

No 1,478 47

Vot

ed V

VD

No 1,611 32

Yes 154 216 Yes 113 139

Maximum likelihood estimation with binary logistic regression

The binary logit model with vote in the election for a party as dependent variable; frequency

of watching public broadcasting, frequency of watching commercial broadcasting, reading

certain newspapers and the estimation of the number of seats that party will get in the election

as independent variables; age, sex, education, income and religiosity as control variables; and

finally the intention to vote for that party a few weeks before as lagged dependent variable,

reduces the error in the prediction of the binary variable with 56.6 % for the model with

voting for the PvdfA as dependent variable and with 50.0 % for the model with voting for the

VVD as dependent variable according to the adjusted count R2. The results of these models

can be found in Table 3.

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Table 2. The effects of the independent variables on the odds of having voted for a party (PvdA/VVD)PvdA vote VVD vote

Odds ratios (SE) Odds ratios (SE)Intention to vote for this party (1 =Yes, 0 = No) 75.336 (23.187)** 65.049 (21.027)**

Watching public broadcasting 1.404 (0.249) # 0.915 (0.172)

Watching commercial broadcasting 1.046 (0.189) 0.923 (0.182)

Reading De Telegraaf (1 = Yes, 0 = No) 0.539 (0.171) ## 2.673 (0.729)**

Reading De Volkskrant (1 = Yes, 0 = No) 1.054 (0.353) 0.488 (0.208)

Reading Algemeen Dagblad (1 = Yes, 0 = No) 0.923 (0.291) 1.716 (0.521)

Reading NRC Handelsblad (1 = Yes, 0 = No) 0.773 (0.304) 1.450 (0.534)

Estimated number of seat for party 1.044 (0.019)* 0.998 (0.020)

Age 0.985 (0.008) 0.982 (0.009)**

Male (1 = Yes, 0 = No) 0.664 (0.157) 0.915 (0.236)

Low level education (ref. Middle) 0.904 (0.327) 0.641 (0.266)

High level education (ref. Middle) 0.876 (0.240) 0.870 (0.252)

Income 1.012 (0.023) 1.037 (0.024)

Religious (1 = Yes, 0 = No) 0.590 (0.142)* 0.572 (0.146)*

Observations (N) 973 904Adjusted count R2 / Nagelkerke R2 0.566 / 0.564 0.500 / 0.525χ2 430.00 340.98BIC -6043.753 -5566.993Cells contain odd ratios, exp(b); with standard errors in parentheses # p = 0.056, # p = 0.052,* p < 0.05, ** p < 0.01

The exponentials of the coefficients estimated by the binary logit models, odds ratios, indicate

that whether variables positively (coefficients above 1) or negatively (coefficients below 1)

affect the likelihood that a respondents votes for a party. Logically, the effects of the lagged

dependent variable ‘Intention to vote for this party’ are large and positive, more interesting

are the other effects.

Starting with the first hypothesis, watching more frequently public broadcasting makes

it more likely that respondent have voted for the PvdA, whereas this has no influence on the

likelihood of voting for the VVD. A one-point increase in watching public broadcasting raises

the odds of voting for the PvdA by a factor of 1.404, holding the other variables constant.

Following a two-tailed test with 95% confidence interval, this effect is not significant;

however, because this effect was hypothesized to be positive, a one-tailed test is allowed and

it is thus possible to conclude that watching programs of public broadcasters makes

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respondents more likely to vote for the PvdA (χ2 = 3.66, p = 0.06) compared to their intention

a few weeks before the elections. As expected, watching commercial broadcasting has no

significant effects on the likelihood of voting for one of the two parties.

De Telegraaf is the only print medium that has a significant effect on the votes. When

we inspect the coefficients belonging to reading the newspapers included in the analysis, it

becomes clear that reading all the other newspapers does not significantly increase or decrease

the likelihood of voting for the PvdA or the VVD. However, reading De Telegraaf does this

and also in the direction that was expected, therefore again one-tailed tests were allowed.

Reading De Telegraaf significantly raises the odds of voting for the VVD by a factor of 2.673

(χ2 = 13.00, p < 0.01), whereas it significantly decreases the odds of voting for the PvdA by a

factor of 0.539 (χ2 = 3.78, p = 0.052). The hypothesised effects of reading De Volkskrant were

rejected as it seems not to influence the odds of voting for the PvdA significantly (χ2 = 0.02, p

= 0.88) and the effect on the odds of voting for the VVD was only marginally significant (χ2 =

2.83, p = 0.09). However, this last effect was indeed in the expected direction, as reading De

Volkskrant decreases the odds of voting VVD by a factor of 0.488.

Finally, the so-called bandwagon effect seems only to be found partially by this

analysis. It seems only for the PvdA vote the case that as higher respondents expect the

number of seats that party will get after the election, the more likely it will become they vote

for the PvdA. For every one seat higher estimation of the election results, the odds of voting

for the PvdA significantly increases by a factor of 1.044 (χ2 = 5.83, p < 0.05). A similar effect

was not found for the VVD voters (χ2 = 0.01, p = 0.94).

ConclusionThis study has found some interesting results. First of all, the stimulating influence of

watching public broadcasters’ programs on the intention to vote for the PvdA. The likelihood

of this increases by seeing those programs and as this study controls for many possible

confounding variables, this might indicate certain content in those programs that are

favourable for the PvdA and perhaps other left-wing parties too. This is remarkable since of

the programs that were taken into consideration, only two of the eight were produced by the

VARA, a public broadcaster that is related to the PvdA in various ways. Therefore, other

characteristics of those programs might explain why watching these programs increases the

odds of voting for the PvdA, but does not influence the odds of voting for the VVD. A similar

but contradictory conclusion is that reading De Telegraaf increases the odds of voting for the

VVD, while it decreases the odds of voting for the PvdA. Probably a characteristic of this

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newspaper underlies this effect. To understand both effects better, content analysis might be

helpful. Nevertheless, the results seem to confirm the left-wing identity of the public

broadcasting system and the right-wing identity of De Telegraaf. It was not possible to

conclude straightforwardly whether a bandwagon effect took place in this study. While it

seems a cause for voting the PvdA, the estimation of the number of seats the VVD gets in the

election did not influence the final vote for that party.

Though results could possibly be biased by sensitization to the questions (Romer,

Kenski, Winneg, Adasiewicz & Jamieson, 2006), the two-wave panel design had the large

benefit that it was possible to include a lagged dependent variable, and thereby control for the

past political preferences of respondents. Therefore, we can be surer that the respondents were

influenced by the media in the weeks between the two measures, in which it is also likely,

because there probably was a lot of media attention for politics as the elections were coming

near. This influence seemed to be in the direction that was expected for the public

broadcasting programs and De Telegraaf and the assumptions that are often expressed about

these can therefore be substantiated with the results of this study.

ReferenceMcAllister, I., & Studlar, D. T. (1991). Bandwagon, underdog, or projection?: Opinion polls

and electoral choice in Britain, 1979-1987. The Journal of Politics, 53, 720-740.

Romer, D., Kenski, K., Winneg, K., Adasiewicz, C., & Jamieson, K. H. (2006). Capturing

campaign dynamics 2000 & 2004: The National Annenberg Election Survey.

Philidelphia: University of Pennsylvania Press.

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Appendix A: Television programs used to construct the independent variables

Public broadcasting Commercial broadcasting

Onderweg naar morgen (Ned. 3) Goede Tijden, Slechte Tijden (RTL4)

EenVandaag (Ned. 1) Editie NL (RTL4)

De Wereld Draait Door (Ned. 3) Boulevard (RTL4)

Man Bijt Hond (Ned. 2) Big Brother (Talpa)

NOS 8 uur journal (Ned. 1) RTL4 Nieuws (RTL4)

NOVA, Den Haag Vandaag (Ned. 2) Hart van Nederland (SBS6)

Netwerk (Ned. 2) Shownieuws (SBS6)

Pauw en Witteman (Ned. 1) Jensen! (RTL5)

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Appendix B: Do File*Assignment8clearset memory 250m, permanentlyset more off, permanentlyuse H:\DDA\NKO2006

tab v081 tab v081, nol gen pvda2006intention = 0replace pvda2006intention = 1 if v081==2gen vvd2006intention = 0replace vvd2006intention = 1 if v081==3

tab v512tab v512, nolgen pvda2006vote = 0replace pvda2006vote = 1 if v512==2gen vvd2006vote = 0replace vvd2006vote = 1 if v512==3

//all measures have a 911 out of 2806 people get the answer PA(means not measured in this wave), those will therefore be droppeddrop if v936==994

****Media independent variables*programs on commercial televisiontab v868tab v853tab v854tab v859tab v861tab v863tab v864tab v870tab v868, noltab v853, noltab v854, noltab v859, noltab v861, noltab v863, noltab v864, noltab v870, nol

replace v868=.a if v868==997replace v853=.a if v853==997replace v854=.a if v854==997replace v859=.a if v859==997replace v861=.a if v861==997replace v863=.a if v863==997replace v864=.a if v864==997replace v870=.a if v870==997

pwcorr v868 v853 v854 v859 v861 v863 v864 v870egen commtv = rowmean(v868 v853 v854 v859 v861 v863 v864 v870)egen commtv_m = rowmiss(v868 v853 v854 v859 v861 v863 v864 v870)replace commtv = .a if commtv_m>3sum commtv tab commtv , misshistogram commtv graph box commtv

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*programs on public broadcasting tvtab v857tab v852tab v860tab v855tab v867tab v871tab v856tab v872tab v857, noltab v852, noltab v860, noltab v855, noltab v867, noltab v871, noltab v856, noltab v872, nol

replace v857=.a if v857==997replace v852=.a if v852==997replace v860=.a if v860==997replace v855=.a if v855==997replace v867=.a if v867==997replace v871=.a if v871==997replace v856=.a if v856==997replace v872=.a if v872==997

corr v857 v852 v860 v855 v867 v871 v856 v872pwcorr v857 v852 v860 v855 v867 v871 v856 v872alpha v857 v852 v860 v855 v867 v871 v856 v872

egen pbstv = rowmean(v857 v852 v860 v855 v867 v871 v856 v872)egen pbstv_m = rowmiss(v857 v852 v860 v855 v867 v871 v856 v872)replace pbstv = .a if pbstv_m>3sum pbstv tab pbstv , misshistogram pbstv graph box pbstv

***Other media variables***tab v016tab v016, nolrecode v016 (1=1 Yes) (2=0 No) (997=.a) (998=.a) (999=.a), gen(Telegraaf)tab Telegraaf

tab v017 tab v017, nolrecode v017(1=1 Yes) (2=0 No) (997=.a) (998=.a) (999=.a), gen(Volkskrant)tab Volkskrant

tab v019 tab v019, nol recode v019(1=1 Yes) (2=0 No) (997=.a) (998=.a) (999=.a), gen(NRC)tab NRC

tab v020tab v020, nol recode v020(1=1 Yes) (2=0 No) (997=.a) (998=.a) (999=.a), gen(AD)tab AD

**************Prepare the other independent variables *******

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tab v104 tab v104 , nolreplace v104=.a if v104==997|v104==998tab v104, missinggen estimatePvdASeats=v104

tab v103 tab v103 , nolreplace v103=.a if v103==997|v103==998tab v103, missinggen estimateVVDSeats=v103

tab v421, missgen age = 2006-v421sum agetab age, miss

tab v420, misstab v420, nolabelrecode v420(2=0 Female) (1=1 Male), gen(male)tab male,miss

*highest education completedtab v430tab v430, nolrecode v430(1=0 elementary) (2=1 vocational) (3=2 secondary) (4=3 higherLevel) (5=4 university) (997=.a), gen(education)tab v430tab education, misstab education, nol

gen loweducation=0replace loweducation=1 if education==0|education==1replace loweducation=.a if education==.a

gen middleeducation=0replace middleeducation=1 if education==2|education==3replace middleeducation=.a if education==.a

gen higheducation=0replace higheducation=1 if education==4replace higheducation=.a if education==.a

tab loweducation,misstab middleeducation,misstab higheducation,miss

*household income corrected for hh sizetab v414, misstab v414, nolgen income=v414replace income=.a if income==998tab income

tab v425tab v425, nolrecode v425(2=0 notReligious) (1=1 Religious), gen(religious)tab religious, missreplace religious=.a if religious==997tab religious, misstab religious, nol

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logit pvda2006vote pvda2006intention commtv pbstv NewspaperT1 NewspaperT2 Telegraaf Volkskrant NRC AD Metro Spits EncounterPollsT1 EncounterPollsT2 seenDebatesEntirely seenNoDebates MatchmakerPVDA MatchmakerSP estimatePvdASeats Turkey_EU age male loweducation higheducation income religious

*Just AR(1)logit pvda2006vote pvda2006intentionlistcoef

*AR(1) plus controlslogit pvda2006vote pvda2006intention age male loweducation higheducation income religiouslistcoef

*AR(1) plus controls plus tvlogit pvda2006vote pvda2006intention commtv pbstv age male loweducation higheducation income religiouslistcoef

*AR(1) plus controls plus tv plus newspaperlogit pvda2006vote pvda2006intention commtv pbstv Telegraaf Volkskrant AD NRC age male loweducation higheducation income religiouslistcoef

**diagnosticspredict rstd, rslabel var rstd "Standardized Residual"sort rstd , stablelist rstd rnr pvda2006vote pvda2006intention commtv pbstv Telegraaf age male loweducation higheducation income religious if (rstd>2.5|rstd<-2.5)&rstd!=.predict cook, dbetagraph twoway scatter cook rnr, ylabel(0(.01).05) xtitle("RNR") yline(.1 .2) msymbol(none) mlabel(rnr) mlabposition(0)list pvda2006vote pvda2006intention commtv pbstv Telegraaf Volkskrant AD NRC age male loweducation higheducation income religious estimatePvdASeats Turkey_EU if rnr==4078|rnr==1729|rnr==3366

//remove uncredible estimates of pvda seatstab estimatePvdASeats replace estimatePvdASeats =.a if estimatePvdASeats<10replace estimatePvdASeats =.a if estimatePvdASeats>60tab estimatePvdASeats

tab estimateVVDSeatssum estimateVVDSeatsreplace estimateVVDSeats=.a if estimateVVDSeats<10replace estimateVVDSeats=.a if estimateVVDSeats>40tab estimateVVDSeats

logit pvda2006vote pvda2006intention commtv pbstv Telegraaf Volkskrant AD NRC estimatePvdASeats age male loweducation higheducation income religious

drop rstd cookpredict rstd, rslabel var rstd "Standardized Residual"sort rstd , stablelist rstd rnr pvda2006vote pvda2006intention commtv pbstv Telegraaf age male loweducation higheducation income religious if (rstd>2.5|rstd<-2.5)&rstd!=.predict cook, dbetagraph twoway scatter cook rnr, ylabel(0(.01).05) xtitle("RNR") yline(.1 .2) msymbol(none) mlabel(rnr) mlabposition(0)

v

list cook rstd pvda2006vote pvda2006intention commtv pbstv Telegraaf Volkskrant AD NRC age male loweducation higheducation income religious estimatePvdASeats Turkey_EU if rnr==1797|rnr==1717|rnr==1729|rnr==1228|rnr==1927|rnr==2751

*test for heteroscedasticityhetprob pvda2006vote pvda2006intention commtv pbstv Telegraaf Volkskrant AD NRC age male loweducation higheducation income religious estimatePvdASeats, het(pvda2006intention commtv pbstv Telegraaf Volkskrant AD NRC age male loweducation higheducation income religious estimatePvdASeats)* not significant, no heteroscedasticity, so robust estimation is not necessary

*test for multicollinaritycollin vvd2006vote vvd2006intention pbstv commtv Telegraaf Volkskrant AD NRC estimateVVDSeats age male loweducation higheducation income religious

**check for wrong codingstab pvda2006vote, nol tab pvda2006intention , noltab commtv , noltab pbstv , noltab Telegraaf , noltab Volkskrant , noltab AD , noltab NRC , noltab age , noltab male , noltab loweducation , noltab higheducation , noltab income , noltab religious , noltab estimatePvdASeats , noltab Turkey_EU, noltab vvd2006vote , noltab vvd2006intention , noltab estimateVVDSeats

*inspection of changetab pvda2006vote pvda2006intention tab vvd2006vote vvd2006intention

**Final modelslogistic pvda2006vote pvda2006intention pbstv commtv Telegraaf Volkskrant AD NRC estimatePvdASeats age male loweducation higheducation income religious fitstattest pbstv test Telegraaf test Volkskrant test estimatePvdASeats

logistic vvd2006vote vvd2006intention pbstv commtv Telegraaf Volkskrant AD NRC estimateVVDSeats age male loweducation higheducation income religious fitstattest pbstvtest Telegraaftest Volkskranttest estimateVVDSeats

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