ELEMENTS ELEMENTS OF OF

DEMOGRAPHDEMOGRAPHYYIsaac A. Ilano, MSPH Isaac A. Ilano, MSPH

Associate Professor Associate Professor Department of Department of Family and Community MedicineFamily and Community Medicine

DEMOGRAPHYDEMOGRAPHY - - is the mathematical is the mathematical and statistical study of the size (# of and statistical study of the size (# of persons in a population), composition persons in a population), composition (measurable characteristics) and (measurable characteristics) and spatial distribution (arrangement of the spatial distribution (arrangement of the population in space in a given time) of population in space in a given time) of human populations, and of changes human populations, and of changes over time in these aspects, through the over time in these aspects, through the operation of the five processes of:operation of the five processes of:- Fertility- Fertility - - no. of children being bornno. of children being born– Mortality Mortality - deaths - deaths– Marriage Marriage - age of getting married- age of getting married– Migration Migration - in and out migration- in and out migration– Social mobilitySocial mobility

USES OF USES OF DEMOGRAPHIC DEMOGRAPHIC

DATADATA

To determine the number and To determine the number and distribution of a population in a distribution of a population in a certain area for planning, certain area for planning, priority setting, and for priority setting, and for purposes of fund allocation. purposes of fund allocation.

To determine the growth (or To determine the growth (or decline) and dispersal of decline) and dispersal of population in the past.population in the past.

To establish a “causal To establish a “causal relationship” between relationship” between population trends and various population trends and various aspects of social organization.aspects of social organization.

To predict future developments To predict future developments and their possible and their possible consequences.consequences.

SOURCES OF SOURCES OF DEMOGRAPHIC DATADEMOGRAPHIC DATA

CensusCensus - may be defined as - may be defined as the total process of collecting, the total process of collecting, compiling and establishing compiling and establishing demographic, economic and demographic, economic and social data pertaining, at a social data pertaining, at a specified time or times, to all specified time or times, to all persons in a country or delimited persons in a country or delimited territory. territory.

Essential Features of a Essential Features of a Population Census:Population Census:

Individual enumerationIndividual enumeration - - each individual is enumerated each individual is enumerated separately and the separately and the characteristics of each person characteristics of each person are recorded separately.are recorded separately.

Universality within a defined Universality within a defined territory territory - all people are - all people are includedincluded

Simultaneity –Simultaneity – a population is a population is enumerated enumerated using one reference using one reference date with respect to date with respect to a well a well defined point in timedefined point in time

Periodicity -Periodicity - censuses are taken censuses are taken at regular at regular intervals. Previously, intervals. Previously, every 5 years. every 5 years. Currently, every Currently, every 10 years.10 years.

Types of Census Types of Census Allocation:Allocation:

De jure methodDe jure method - - individuals are assigned to individuals are assigned to the place of their usual the place of their usual residence, without residence, without reference to where they reference to where they were actually enumerated were actually enumerated during the census.during the census.

De facto methodDe facto method - individuals - individuals are allocated to the areas in are allocated to the areas in which they are physically which they are physically present at the census date, present at the census date, without reference to where without reference to where they usually live. they usually live.

Usual Information Obtained Usual Information Obtained in a Census: in a Census:

Geographic informationGeographic information - location at time of - location at time of censuscensusHousehold or family informationHousehold or family information - household/ - household/ family sizefamily sizePersonal characteristicsPersonal characteristics - sex, age, marital - sex, age, marital statusstatusEconomic characteristicsEconomic characteristics - occupation - occupation Cultural characteristicsCultural characteristics - language/s spoken - language/s spokenEducational characteristicsEducational characteristics - literacy, - literacy, educational attainmenteducational attainmentFertility dataFertility data - number of children ever born - number of children ever born

SOURCES OF DEMOGRAPHIC SOURCES OF DEMOGRAPHIC DATA….cont’n.DATA….cont’n.

2.2. Sample Surveys Sample Surveys -- studies done studies done on a subset of a population.on a subset of a population.

3.3. Registration System Registration System -- deals with deals with continuous recording of vital events. continuous recording of vital events. Compulsory of births, deaths and Compulsory of births, deaths and marriages marriages

4. 4. Continuing Population Registers Continuing Population Registers -- continuous recording of information continuous recording of information about the population. about the population.

SOURCES OF DEMOGRAPHIC DATA….cont’n.SOURCES OF DEMOGRAPHIC DATA….cont’n.

Other Record SystemsOther Record Systems– Voter’s RegistrationVoter’s Registration– School EnrollmentSchool Enrollment– Income Tax ReturnsIncome Tax Returns– Social Security SystemsSocial Security Systems

IMPORTANCE OF STUDYING IMPORTANCE OF STUDYING THE AGE AND SEX THE AGE AND SEX COMPOSITION OF A COMPOSITION OF A

POPULATIONPOPULATIONAlmost any measurements that Almost any measurements that can be taken of human beings can be taken of human beings will show substantial variation will show substantial variation by age and sexby age and sex

Ex. Illness and death Ex. Illness and death characteristics are characteristics are affected by age and sex.affected by age and sex.

The age and sex structure of a The age and sex structure of a population is the basic demographic population is the basic demographic determinant of a nation’s manpower determinant of a nation’s manpower supply. It influences requirements for supply. It influences requirements for various essential goods and services.various essential goods and services.

A population’s age and sex structure A population’s age and sex structure is both a cause and an effect. It is both a cause and an effect. It determines the rate of population determines the rate of population growth.growth.

1. THE SEX COMPOSITION OF A 1. THE SEX COMPOSITION OF A POPULATION POPULATION

Tools for describing the sex compositionTools for describing the sex composition No. of malesNo. of males

a.1. a.1. Sex RatioSex Ratio = --------------------------- = --------------------------- x 100x 100

No. of femalesNo. of females > The resulting figure > The resulting figure

represents the number of represents the number of males for males for every 100 females in the population.every 100 females in the population.a.2. a.2. Sex StructureSex Structure = sex ratio for each = sex ratio for each group (life cycle) group (life cycle) Ex. sex ratio for Ex. sex ratio for pre-schoolers, sex ratio for school pre-schoolers, sex ratio for school children, etc. children, etc.

Some generalizations of the Sex Some generalizations of the Sex Composition of a Population:Composition of a Population:

b.1b.1 Sex ratio at birth is generally 105. Sex ratio at birth is generally 105. There are more males than females in the There are more males than females in the younger age group.younger age group.

b.2b.2 The sex ratio tends to decrease with The sex ratio tends to decrease with age, eventually falling below 100. This is age, eventually falling below 100. This is because age- specific mortality rates are because age- specific mortality rates are usually higher among males than usually higher among males than females.females.

b.3b.3 Sex ratio is higher in rural Sex ratio is higher in rural areas than in areas than in urban areas. urban areas. There are less females There are less females and and more males in the rural areas.more males in the rural areas.

b.4b.4 Frontier communities and Frontier communities and colonies have colonies have higher sex ratioshigher sex ratios

2. THE AGE COMPOSITION 2. THE AGE COMPOSITION OF A POPULATIONOF A POPULATION

Tools for Describing the Age Tools for Describing the Age CompositionCompositiona.1a.1 Median Age of the Median Age of the

Population - divides the Population - divides the population into 2 equal parts. It is population into 2 equal parts. It is the age below which 50% of the the age below which 50% of the population fall and above which population fall and above which the rest of the other 50% of the the rest of the other 50% of the population fall.population fall.

a.2a.2 Dependency RatioDependency Ratio - represents - represents the number of the number of dependents that need dependents that need to be supported by every to be supported by every 100 100 population in the working age group.population in the working age group.

Pop’n aged 0-14 + Pop’n Pop’n aged 0-14 + Pop’n aged 65+aged 65+Dependency Ratio = Dependency Ratio = --------------------------------------------- x100--------------------------------------------- x100

Pop’n. aged 15-64Pop’n. aged 15-64The dependency ratio provides an index The dependency ratio provides an index

of the age-induced economic drain on of the age-induced economic drain on manpower resources.manpower resources.

b. Factors Affecting the Age b. Factors Affecting the Age CompositionComposition

b.1 Fertility- a higher fertility b.1 Fertility- a higher fertility leads to a leads to a younger populationyounger population

b.2 Urban- rural differencesb.2 Urban- rural differencesIn general, an In general, an

urban population tends urban population tends to to have an older have an older age age composition than a composition than a rural rural population as a result of the population as a result of the fertility fertility factor.factor.

b.3 Peace and Order Situation (War)b.3 Peace and Order Situation (War) Immediate post-war Immediate post-war

periods bring about a baby periods bring about a baby boom and a boom and a resultant younger populationresultant younger population

b.4 Cultural practices, example, age at b.4 Cultural practices, example, age at marriage. marriage. Women in rural areas get Women in rural areas get married early (at 20 married early (at 20 years old women years old women are already considered old are already considered old maid).maid).

POPULATION PYRAMID POPULATION PYRAMID -- graphical representation graphical representation of the age and sex of the age and sex composition of a composition of a population.population.

1.1.Data NeededData Needed

> > Population distribution by age Population distribution by age and sex and sex

2.2.Compute the percentage falling Compute the percentage falling under each ageunder each age - sex group, - sex group, using the total population as using the total population as the denominator.the denominator.

Steps in Constructing a Steps in Constructing a Population PyramidPopulation Pyramid

Construct the population Construct the population pyramid using the percentages pyramid using the percentages computed. The following computed. The following general rules are followed:general rules are followed:

a. Each group is represented by a. Each group is represented by a a horizontal bar, with horizontal bar, with the first bar at the first bar at the base of the the base of the pyramid representing pyramid representing the the youngest age groupyoungest age group

b.b.The bars for males are traditionally The bars for males are traditionally presented on the left side of the central presented on the left side of the central vertical axis while the bars for females vertical axis while the bars for females are presented are presented on the right side.on the right side.

c. The length of each bar corresponds to c. The length of each bar corresponds to the % of the population falling in the % of the population falling in the specific the specific age and sex group being age and sex group being plotted.plotted.

MALEMALE FEMALEFEMALE

Age group Age group (yrs)(yrs)

No.No. %% No.No. %%

0 – 40 – 45 – 95 – 9

10 – 1410 – 1415 – 1915 – 1920 – 2420 – 2425 – 2925 – 2930 – 3430 – 3435 – 3935 – 3940 – 4440 – 4445 – 4945 – 4950 – 5450 – 5455 – 5955 – 5960 – 6460 – 6465 – 6965 – 6970 – 7470 – 7475 – 7975 – 7980 +80 +

96,98096,98099,76899,76894,03994,03982,97982,97972,58772,58758,66158,66150,73250,73243,30743,30734,96234,96226,66426,66422,36022,36017,61317,61313,61213,61210,08410,0847,8497,8495,9295,9294,5824,582

6.66.66.86.86.46.45.65.64.94.94.04.03.43.42.92.92.42.41.81.81.51.51.21.20.90.90.70.70.50.50.40.40.30.3

91,27191,27193,89393,89388,96288,96278,92678,92669,24169,24156,41156,41149,52349,52342,85242,85235,77335,77328,29628,29624,37324,37319,89519,89515,82015,82013,22613,2269,9599,9597,4897,4896,6056,605

6.26.26.46.46.06.05.45.44.74.73.83.83.43.42.92.92.42.41.91.91.71.71.31.31.11.10.90.90.70.70.50.50.40.4

ALL AGESALL AGES 742,708742,708 50.350.3 732,515732,515 49.749.7

TOTAL POPULATION = 742,708 + 732,515TOTAL POPULATION = 742,708 + 732,515

= 1,475,223= 1,475,223

Number and Percent Distribution of the Population

by Age and Sex, Batangas, 1990

   

Males   Age Females

    80 +  

  75 - 79  

  70 - 74  

  65 - 69  

  60 - 64  

  55 - 59  

  50 - 54  

  45 -49  

  40 - 44  

  35 - 39  

  30 - 34  

  25 - 29  

  20 - 24  

  15 - 19  

  10 - 14  

  5 - 9          0 - 4        

8 6 4 2 0 Percent 0 2 4 6 8

Population Distribution by Age and Sex Batangas, 1990

*Assuming that the oldest person is 100 years old.

Since population pyramids Since population pyramids represent the age and sex represent the age and sex distribution of a population, this distribution of a population, this representation may take on representation may take on various shapes, some of which various shapes, some of which do not resemble a pyramid at do not resemble a pyramid at all. Several types of population all. Several types of population pyramids and their unique pyramids and their unique features are represented by the features are represented by the following figuresfollowing figures

Type 1 pyramid has a broad base and gently sloping sides. This pyramid is typical of countries with high rates of birth and death. The population can also be characterized as having a low median age and high dependency ratio.

Type 2, compared to Type 1, has a broader base and its sides bow in much more sharply as they slant from the 0-4 age group to the top. This second type of pyramid is typical of countries that are beginning to grow rapidly because of marked reduction in infant and child mortality, but are not yet reducing their fertility. As a consequence of a rapidly increasing population, the median age is decreasing.

The third type of pyramid does not resemble a pyramid at all, but an old-fashioned beehive. This age-sex structure is typical of countries with levels of birth and death rates found in the Western European countries. Because of the low birth rates, the median age is highest and its dependency ratio is lowest compared with other age-sex structures. The dependents are mostly elderlies.

The fourth type of pyramid, a bell-shaped one, is a transitional type of pyramid. This represents a population which, after more than 100 years of declining birth and death rates, has reversed the trend in fertility while maintaining the death rate at low levels.

The last type of population pyramid represents a population which is experiencing a marked and rapid decline in fertility. If this decline continues, however, the absolute loss in numbers will soon become apparent. The population represented by this pyramid has usually a low death rate and as mentioned above, has reduced its birth rate very rapidly

CONSEQUENCES/ EFFECTS CONSEQUENCES/ EFFECTS OF AGE OF AGE

AND SEX STRUCTUREAND SEX STRUCTURE

1. Consumption Patterns - If the 1. Consumption Patterns - If the population has a population has a large proportion large proportion of children, there is a need for of children, there is a need for greater spending on food and greater spending on food and education. On the education. On the other hand, a other hand, a large proportion of old persons large proportion of old persons necessitate greater spending for necessitate greater spending for medical care medical care and social services.and social services.

CONSEQUENCES/ EFFECTS OF AGE AND SEX CONSEQUENCES/ EFFECTS OF AGE AND SEX STRUCTURE…cont’n.STRUCTURE…cont’n.

2. Death rate is affected by age structure. 2. Death rate is affected by age structure. A younger population has a lower Crude A younger population has a lower Crude Death Rate.Death Rate.

3. Migration rates. Young adults tend to be 3. Migration rates. Young adults tend to be more more mobile than middle aged and mobile than middle aged and elderly personselderly persons

4. Variations in age and sex structure affect 4. Variations in age and sex structure affect the the probabilities of marriage for men probabilities of marriage for men and womenand women

5. Power structure. An older population is 5. Power structure. An older population is usually more conservative.usually more conservative.

OTHER IMPORTANT OTHER IMPORTANT POPULATION POPULATION

CHARACTERISTICSCHARACTERISTICS1.1. Marital status - affects fertility Marital status - affects fertility and mortality and mortality rates. The greater the rates. The greater the population of married population of married women, the women, the higher the Crude Birth Rate.higher the Crude Birth Rate.

2.2. Religious composition Religious composition

3.3. Lingual composition Lingual composition

4.4. Economic composition Economic composition

5.5. Educational composition Educational composition

POPULATION POPULATION ESTIMATIONESTIMATION

Tools in Describing Change in Tools in Describing Change in Population SizePopulation Size

a. Natural Increase a. Natural Increase

= number of births -= number of births -number of deathsnumber of deaths

b. Rate of Natural Increase b. Rate of Natural Increase

= CBR - CDR = CBR - CDR

c. Relative Increase in Population Size c. Relative Increase in Population Size (RI) (RI)

= Measures the % increase or = Measures the % increase or decrease in decrease in population count population count relative to an earlier countrelative to an earlier count

Pt – PoPt – Po

RI = --------------- x 100RI = --------------- x 100

PoPo

Where:Where: Pt = population at present Pt = population at present time, ttime, t

Po = population at earlier time, oPo = population at earlier time, o

d. Absolute increase in population d. Absolute increase in population per year (b)per year (b)

Pt – PoPt – Po

b = --------------- x 100b = --------------- x 100

tt

Where: Where:

t = no. of years between t = no. of years between time o time o and and time ttime t

e.e. Annual rate of growth (r)Annual rate of growth (r) = = formula for formula for r r depends on depends on the assumption taken the assumption taken regarding the nature of the regarding the nature of the rate of rate of growth of the growth of the population per year.population per year.

This rate of growth takes on the This rate of growth takes on the assumption that the assumption that the population is changing at a population is changing at a constant rate per year.constant rate per year.

Types of Estimates Types of Estimates and Projectionsand Projections

1. According to detail desired2. According to time reference3. According to Method of Estimation

1. According to Detail 1. According to Detail DesiredDesired

a. Total population vs. a. Total population vs. population population subgroupssubgroups

b. Population by selected b. Population by selected characteristics characteristics (age and sex)(age and sex)

Examples: Estimate nos. of infantsExamples: Estimate nos. of infants

Estimate nos. of mothersEstimate nos. of mothers

2. According to Time 2. According to Time ReferenceReference

a. Intercensal Estimatesa. Intercensal Estimates - refers - refers to a to a date date intermediate to two intermediate to two censuses and take the censuses and take the results of results of these these censuses into account.censuses into account.

b. b. Postcensal EstimatesPostcensal Estimates - refers to a past - refers to a past or or current date following a census and current date following a census and takestakes that census and possibly earlier that census and possibly earlier censuses censuses into account, but not later into account, but not later censuses.censuses.

c. c. Projections Projections - refers to dates following - refers to dates following the last the last census for which no current census for which no current reports are reports are available.available.

The distinction between these two types are The distinction between these two types are not quite clear-cut.not quite clear-cut.

3. According to Method of 3. According to Method of EstimationEstimation

a. a. Component Method (Inflow – Component Method (Inflow – Outflow Method)Outflow Method)

consists of adding natural increase consists of adding natural increase and net migration for the period and net migration for the period since the last census to the latest since the last census to the latest count or the latest previous estimatecount or the latest previous estimate

best implemented where continuous best implemented where continuous population registers are maintainedpopulation registers are maintained

Pt = Po + (B-D) + (I-O)Pt = Po + (B-D) + (I-O)

b.b. Mathematical MethodsMathematical Methods1. Arithmetic Method1. Arithmetic Method

assumes an equal amount of assumes an equal amount of increase every yearincrease every year

2. Geometric Method2. Geometric Method

assumes that the population assumes that the population increases or decreases at a increases or decreases at a constant rate, over each unit of constant rate, over each unit of timetime

3. Exponential Method3. Exponential Method assumes a constant rate of assumes a constant rate of increase increase or decrease, with the or decrease, with the population population size size changing changing continuously at continuously at every every infinitesimal amount of timeinfinitesimal amount of time

assumes population growing assumes population growing by the by the seconds.seconds.

RATIORATIO-- is a relative number expressing the is a relative number expressing the magnitude of one occurrence or condition magnitude of one occurrence or condition in relation to another.in relation to another.

Ex. 1. Sex Ratio

= Number of Males x 100 Number of Females

2. Dependency Ratio = No. of persons aged 0-14 + 65 yrs & over x

100No. of persons aged 15-64

RATERATE-- refers to the occurrence of events refers to the occurrence of events over a given interval of time relative to over a given interval of time relative to the size of the population at risk of the the size of the population at risk of the event during the same time interval.event during the same time interval.

Ex.

Crude Birth Rate (CBR)= No. of live births in a yr. x F

Average Population

It is necessary that the It is necessary that the numerator of the rate numerator of the rate

should be defined should be defined according to:according to:

1.1. the character of the event in the character of the event in question;question;

2.2. the geographical area to which the the geographical area to which the event belongs;event belongs;

3.3. the time period within which it the time period within which it occurred.occurred.

Events should be Events should be tabulated by:tabulated by:

1.1. date of occurrence than by date of date of occurrence than by date of registrationregistration

2.2. by place of residence rather than by by place of residence rather than by place of occurrenceplace of occurrence

Important factors to Important factors to consider in interpreting rate consider in interpreting rate

and ratio:and ratio:1. The source of the numbers that entered 1. The source of the numbers that entered

into the numerator and denominator, into the numerator and denominator, how were they obtained?how were they obtained?

2. Do they represent an accurate count of 2. Do they represent an accurate count of the event under study?the event under study?

3. What is the time period involved? A 3. What is the time period involved? A week? Month? Year?week? Month? Year?

4. Does the rate obtained after 4. Does the rate obtained after analysis measure what it is analysis measure what it is supposed to measure?supposed to measure?

5. Is the magnitude of the rate 5. Is the magnitude of the rate reasonable in relation to what one reasonable in relation to what one may expect the rate to be?may expect the rate to be?

Mortality RatesMortality Rates- measures the probability of dying- measures the probability of dying

Different kinds of Mortality rates:

1. Crude Death Rate (CDR)= Total deaths, all causes x F Average Population

- measure the decrease of the population due to death, the force of

mortality or the probability of dying

Disadvantage:Disadvantage:

not a very useful method of comparing not a very useful method of comparing population groups that are radically population groups that are radically different in composition and may give different in composition and may give misleading conclusions.misleading conclusions.

2. Cause-of-death rate (CSDR)2. Cause-of-death rate (CSDR)= = No. of deaths from a particular causeNo. of deaths from a particular cause

x Fx F

Average PopulationAverage Population

most causes of death rates are computed on total population, except IMR and some age-specific rates.

3. Specific Death Rate:3. Specific Death Rate:- necessary to study in detail the mortality conditions in a community

a)Age-specific-death rate

= Deaths, all causes in particular age grp x F Average population of same age group

b) Age-and-sex specific death rate

= Deaths in partic. age & sex group x F Average pop’n of same age & sex grp.

c) Age-sex & cause-specific death rate

= Deaths from partic. cause in sex & age group x F Ave. pop’n of same age & sex grp

4. Proportionate Mortality 4. Proportionate Mortality raterate

- this rate may be cause, age, sex, occupation - this rate may be cause, age, sex, occupation etc.etc.- used for describing the relative importance of

different fatal diseases in the population, of different ages, sex, occupation, etc.- can be calculated for specific age group

useful for determining the order of importance of cause of death in different age groups.

denominator: total death all causesdenominator: total death all causes

Swaroop’s Index:

- the higher this rate the better is the health status of the population

- this is a good indicator in comparing the health status of different countries,

since it is very simple and most of the information needed are available.

total deaths 50 yrs old & above

total death, all causes SI - X 100

5. Infant Mortality Rate 5. Infant Mortality Rate (IMR)(IMR) = = No. of deaths below 1 yrNo. of deaths below 1 yr x F x F

No. of livebirthsNo. of livebirths

- one of the most sensitive indices of the health condition of the general population

6. Neonatal-Mortality Rate 6. Neonatal-Mortality Rate (NMR)(NMR)

= = No. of deaths below 28 daysNo. of deaths below 28 days x F x F

Total livebirthsTotal livebirths

- deaths in this period are mostly due to prenatal causes and are more difficult to reduce than the post-neonatal death rate

7. Post-Neonatal Mortality 7. Post-Neonatal Mortality Rate (PNMR)Rate (PNMR)

= = Infant deaths 28 days to<1yrInfant deaths 28 days to<1yr x F x F

Total livebirthsTotal livebirths

= Fetal deaths 28 wks. & over gestation x FTotal livebirths

8. Fetal Death Ratio (Stillbirth rate)

9. Perinatal Mortality Rate9. Perinatal Mortality Rate= = Fetal deaths, 28 wks & over gestation + Fetal deaths, 28 wks & over gestation +

infant deaths < 7 daysinfant deaths < 7 days x F x F

Total livebirthsTotal livebirths

= Deaths among women directly due to pregnancy, labor & puerperium x F

Total livebirths

10. Maternal Mortality Rate

measure the risk of dying from causes measure the risk of dying from causes associated with childbirthassociated with childbirth

ideal denominator in the number of ideal denominator in the number of women but since this number is unknown, women but since this number is unknown, the number of livebirths has been adopted the number of livebirths has been adopted for practical reasons.for practical reasons.

caution must be exercised in comparing caution must be exercised in comparing this rate from different places.this rate from different places.

11. Case Fatality Rate11. Case Fatality Rate

= = No. of deaths from a particular No. of deaths from a particular diseasedisease x F x F

No. of cases of same diseaseNo. of cases of same disease

- modified by the completeness of both reported cases and deaths.

- refers to diseases or sickness- refers to diseases or sickness

Morbidity RatesMorbidity Rates

Two general types of Morbidity Rates:

1. Incidence Rate = No. of New Cases of Dse. over a prd. of time x F

Population at risk- this is a broad term & the figures in the numerator is usually obtained from notification during an interval of time, usually a year and hence are usually underenumerated

2. Prevalence Ratio2. Prevalence Ratio= = No. of existing old & new cases at a point in timeNo. of existing old & new cases at a point in time x F x F

Total PopulationTotal Population

- this is a static count of the number of individuals suffering from a particular disease in a particular instant of time

Fertility RatesFertility RatesMost commonly used of fertility rates are:Most commonly used of fertility rates are:

= No. of livebirths in a year x FAverage Population

1. Crude Birth Rate (CBR)

• this rate gives the number of livebirths relative to the total population• data is always available widely used

2. General Fertility Rate 2. General Fertility Rate (GFR)(GFR)

= = No. of livebirths in 1 yearNo. of livebirths in 1 year x F x F

No. of Women 15-44 yrsNo. of Women 15-44 yrs

- more appropriate measure of fertility

Thank YouThank Youand and

God Bless!God Bless!