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Measuring Fertility Two types of measures

Period measures

Cohort measures Cohort - a group who experiences a

demographic event at the same time Birth cohort; marriage cohort; graduating class; etc.

Period - a combination of cohorts in a givenyear or other period. A snapshot of all cohorts at one point in time.

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Fertility The principle Period measures are:

The Crude Birth Rate (CBR)

The General Fertility Rate GFR) The Child Woman Ratio (CWR)

Coales Index of Fertility (Coales Index If)

The Age-Specific Fertility Rate (ASFR)

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Fertility The Cohort Measures

The Total Fertility Rate (TFR)

The Gross Reproduction Rate (GRR) The Net Reproduction Rate NRR)

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Crude Birth Rate (CBR)

Doesnt take into account age structure

gender balance

marriage rates

Uses vital statistics (births) and census data(population)

1000midyearatPopulation

yeargivenainBirthsv!CBR

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World30.shp

Crude Birth Rates8.03 - 14.85

14.85 - 22.41

22.41 - 28.9528.95 - 39.29

39.29 - 50.68

N

EW

S

Crude Birth Rates

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CBR: Uni States

0

5

10

15

20

25

30

1930 1940 1950 1960 1970 1980 1990 2000 2010

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General Fertility Rate (GFR)

The fertility rate.

15-44 considered the children bearing years.

Tends to be about 4.5 times CBR.

Requires vital statistics and census data.

An improvement over CBR, but more detailed data

required.

1000

44-15ageW

omen

yearainirthsv!GFR

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Child Women Ratio (CWR)

Extends age range in denominator to account for the fact that

some kids are now 4 (possibly born when mother was 45).

Range: About 200 to over 1000.

Approx. 4.5 times GFR. 1990: 279 in the US, 489 in Mexico.

Advantage: Census data only.

1000

49-15ageW

omen

4-0agePopulationv!CWR

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Measuring Fertility

Compute for each age group, x to x+5.

So we have a set orschedule of age

specific rates.

Requires age and sex information but

controls for the age-sex structure of a

population.

10005xx toageWomen

5xx toagewomenyear toainirthsv

!ASFR

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US ASFR

0

50

100

150

200

250

300

0 2 4 6 8

1960

2002

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A R 2003: U and Ethiopia

0

50

100

150

200

250

300

15-

19

20-

24

25-

29

30-

34

35-

39

40-

44

45-

49

Eth o p a

Un tedState

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Total Fertility Rate (TFR)

Multiplied by 5 only if 5-year age intervals. 2 for 2-year intervals , and so on.

Occasionally expressed per 1000. Most often applied as period measure to create

a synthetic cohort.

1000

5, !

x

xASFRx

TFR

1000

55, v

!x

xxASFR

TFR

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Gross Reproduction Rate (GRR)

Number of female children a women may

expect to have in her lifetime if her fertility

follows current fertility rates and she

survives through childbearing years.

BirthsAll

BirthsemaleTFRv!GRR

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Lo TFRCountries

Countr orarea atio /

Bul aria 1.133 0.550 0.4854Czech epublic 1.182 0.574 0.4859

Lat ia 1. 02 0.587 0.4878

Singapore 1. 40 0.597 0.4813

Hungar 1. 50 0.603 0.4827

Slov

akia 1. 50 0.609 0.4870

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High TFRCountries

Country TF G tio G /TF

M li . . .Congo (Kinshasa) . . .

ganda . . .

Y m n . . .

Niger . . .

omalia . . .

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Net Reproduction Rate (NRR) Like the GRR, but takes into account the

mortality rates of women.

Slightly smaller than GRR. Value of 1 indicates that the population will

eventually quit growing or shrinking.

Less than 1, population will shrink. Greater than 1, it will grow.

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The Coale (Princeton) Fertility Index (If)

Births are compared to fertility of the Hutterite population

B is the number of births in a given year

wi is the number of women in the population at age i

fi is the age specific fertility rate of Hutterite woment atage i

Need births in a given year and age distribution ofwomen

!

i

ii

ffw

BI

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Cohort Measures of Fertility Children Ever Born

How many children born alive by the end of a

cohorts childbearing years? Average for cohort often reported.

Retrospective surveys often used to elicit this

expensive and cant get the data until the

childbearing years are over.

Fertility Intention Surveys