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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