5- Fertility Measures

8/2/2019 5- Fertility Measures

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Fertility Measures

Prof. Maria Paz N. Marquez

Training Course on Basic DemographyRichville Hotel, Mandaluyong City


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Definition of terms

The definitions are reversed in the Romance languages.

E.g., In Spanish: Fertility = FecundidadFecundity = Fertilidad

Fertility Actual birth performance

Fecundity Physiological capacity of a woman, man orcouple to reproduce


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Definition of terms

Livebirths

The complete expulsion from its motherthe product of conception, irrespective ofthe duration of pregnancy, which after

such separation, breathes or shows anyother evidence of life such as beating ofthe heart, pulsation of the umbilicalcord, or definite movement of voluntarymuscles, whether or not the umbilical

cord has been cut or the placenta isattached, each product or such a birth isconsidered live-born.


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Measures of Fertility

Crude birth rate (CBR)

General fertility rate (GFR)

Age-specific fertility rate (ASFR) Total fertility rate (TFR)

Gross reproduction rate (GRR)

Net reproduction rate (NRR)

Children ever born (CEB)

Child woman ratio (CWR)


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Crude birth rate

where B

y

= No. of births in year yPy = Midyear population in year y

k = Any number, usually 1,000

kP

BCBR

y

y


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Crude birth rate

The simplest measure of fertility and the easiest to

calculate.

Why crude?

Because its denominator, includes many people

who are not at the risk of childbearing, e.g.,women in the ages < 15 and > 49, and men.


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General fertility rate

A more refined measure than the CBR since it

restricts the denominator to women of

childbearing ages.


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General fertility rate

where By = No. of births in year y

W15-49

y = Midyear population of

women 15-49 years old in

year y


k

W

BGFR

y

y

4915


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Age-specific fertility rates

where B = Births to women of age group i

W = Midyear population of women in age group i

i = Age group from 1 (15-19) to 7 (45-49)

000,1i

i

i

W

BASFR


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Age-specific fertility rates, 1970-2006


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Total Fertility Rates

7

1

5i

iASFRTFR

where: ASFRi = Age-specific rate for age group ii = Age group from 1 (15-19) to 7 (45-49)

means one should add up the age-specific rates


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Computing the TFR

Age group

(A)

1990

Midyear

Population

(B)

1990

Births

(C)

1990

ASFR

(C)(B)

(D)

15-19 3,334,851 166,743 0.050

20-24 2,915,284 553,904 0.190

25-29 3,497,266 541,907 0.155

30-34 2,099,718 380,049 0.181

35-39 1,740,925 208,914 0.120

40-44 1,370,176 69,879 0.05145-49 1,113,170 8,905 0.008

Total 0.755


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TFR: Advantages/ Disadvantages

Because nobody lives their whole lives stuck in one

year, the TFR does not reflect actual experience.

One year of low fertility does not mean a wholegeneration of women will have low fertility.

If women begin delaying births, the TFR will

indicate fewer births.

It is easy to interpret.

It is a fairly stable all-purpose

measure.


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Interpreting the TFR

The TFR is the number of children that would be

born alive to a woman during her lifetime if she

were to pass through her childbearing yearsconforming to the age-specific fertility rates of a

given period.

TFR = 2 2 children per woman


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Trends in the TFR: 1973-2008

Source: NSO and ICF Macro, 2009


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Gross reproduction rate

100

206GRR = x TFR

where: 100/206 = The proportion female among

live births


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Gross reproduction rate

Similar to TFR except that it is the sum of age-specific rates that include only female life birthsin the numerator.

The GRR measures the extent to which ahypothetical cohort of women will replace

itself, provided no women die in the childbearingyears.


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Net reproduction rate

A measure of the number of daughters who willbe born to a hypothetical cohort of women,taking into account the mortality of the womenfrom the time of their birth.

Those interested to compute for the NRR have to

study the technicalities involved in life tablepreparation.


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Training Course on Basic Demography

Richville Hotel, Mandaluyong City

Children ever born

Derived by asking women the numberof children they ever had

Usually tabulated by womans age

yielding cumulative fertility of womenup to specified points in theirchildbearing years

Limitations:

o Measures past fertilityo Children who died young may not be

remembered


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Mean no. of CEB among women 15-49:

2008 NDHS

Source: NSO and ICF Macro, 2009


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Child-woman ratio

where P0-4 = Population 0-4 years oldW15-49

= Women 15-49 years old


k

W

PCWR

4915

40


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Advantages of CWR

Does not require a special question in the census.

Useful means of obtaining fertility statistics for

small areas

Can be computed for certain groups of the

population where classification of the mother

and child by the given characteristic would bethe same.


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Disadvantages of CWR

Directly affected by underenumeration of youngchildren.

Affected by mortality. Since survival rate is higheramong women than children under 5, the ratiosalways understate recent fertility.

Population 0-5 refers to the survivors not the actual birthsoccurring in the last five years thus the ratio is likely to

understate actual fertility If we use ages 5-9 because they are better enumerated,

this aggravates the problem because it refers to fertility 7.5years before the census (thus not a good measure ofcurrent fertility)


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Which group of

women in the worldhave the highest

fertility?


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The Hutterites:

Champions of high fertility

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Fertility ratesWomens

age

Hutterite

women

(1936-1940)

USA women

(1940)

15-19 259 136

25-29 466 123

30-34 462 83

35-39 431 46

40-44 203 16

45-49 48 2

27


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Contraceptive Prevalence Rate (CPR)

Numerator: Number of Married Women, aged 15-49, in year y, area aDenominator: Total number of Married Women 15-49, in year y, area a

The CPR is expressed as the percentage of women currently using any family

planning (FP) method among currently married women in the ages 15-49 years.


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Time to do some

exercises!


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Age

Number of

women,May 1, 1990

Adjusted

number ofwomen,

July 1, 1990

Birthsin 1990

ASFR

15-19 3,319790 166,743

20-24 2,902,118 553,904

25-29 2,485,988 541,907

30-34 2,090,235 380,049

35-39 1,733,089 208,914

40-44 1,363,988 69.879

45-49 1,108,143 8,905

TOTAL 15,003.351 1,930,301

COMPUTING ASFR:


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Age ASFR

ASFR X

proportion ofbirths female

(0.4902)

15-19 50

20-24 190

25-29 217

30-34 181

35-39 120

40-44 51

45-49 8

SUM

SUM X 5= GRR (per 1000 women)

COMPUTING GRR:


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Thank You!

Documents

5- Fertility Measures