Fertility Its calculation Dostogir Harun Assistant Professor Department

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Fertility &Its calculation Dostogir Harun Assistant Professor Department of Public Health, DIU Email: dostogirharun@gmail.

Fertility &Its calculation Dostogir Harun Assistant Professor Department of Public Health, DIU Email: dostogirharun@gmail. com Cell: 01556 636 545

Fertility & Fecundity Fertility refers to the actual reproductive performance of a population, based

Fertility & Fecundity Fertility refers to the actual reproductive performance of a population, based on the number of live births that occur. or the number of live births a woman has actually had Fecundity The physiological capability to reproduce. So fecundity refers to the potential production, and fertility to actual production, of live offspring. Still births, fetal deaths and abortions are not included in the measurement of fertility in a population

Fertility & Fecundity • It is thought that the maximum number of children an

Fertility & Fecundity • It is thought that the maximum number of children an average woman can theoretically produce is about fifteen if she starts childbearing as soon as possible after menarche • According to the Guinness Book of Records, the greatest number ever officially recorded is sixty-nine by a woman living near Moscow during the eighteenth century (sixteen pairs of twins, seven sets of triplets and four sets of quadruplets). • The highest recorded average for any population is about ten births per woman among the Hutterites

Definitions • Reproductivity -Extent to which a group is replacing its own number by

Definitions • Reproductivity -Extent to which a group is replacing its own number by natural process • Parity—Number of children born alive to a woman • Birth interval—Time between successive live births • Pregnancy interval—Time pregnancies of a woman between successive

Measuring Fertility • C/W ratio- The Child/Woman Ratio • CBR – crude birth rate

Measuring Fertility • C/W ratio- The Child/Woman Ratio • CBR – crude birth rate • GFR – general fertility rate • ASFR – age specific fertility rate • TFR – total fertility rate • GRR- Gross Reproduction Rate • NRR- Net Reproduction Rate

The Child/Woman Ratio • Ratio of children less then 5 years per thousand women

The Child/Woman Ratio • Ratio of children less then 5 years per thousand women of child bearing age P 0 -4 C/W Ratio = -------- X 1000 W 15 -49 P 0 -4 = the number of children less than 5 years W 15 -49 =the number of women aged 15 -49 years

Exercise: C/W Ratio Use the following data to calculate the CWR Household population composition

Exercise: C/W Ratio Use the following data to calculate the CWR Household population composition by age and sex, Kenya 1998 Age group Male Female Total 0 -4 268873 256705 525578 … 15 -19 189272 192067 381340 20 -24 130899 158825 289723 25 -29 116747 142204 258951 30 -34 100827 99727 200555 35 -39 88445 103421 191866 40 -44 67218 68332 135550 45 -49 57800 58020 115820

Solution P 0 -4 C/W Ratio = -------- X 1000 W 15 -49 525578

Solution P 0 -4 C/W Ratio = -------- X 1000 W 15 -49 525578 = -------- X 1000 822596 = 638. 9 children 0 -4 per 1, 000 women 15 -49

The C/W Ratio • This ratio is used where birth registration statistics either do

The C/W Ratio • This ratio is used where birth registration statistics either do not exist or are inadequate. • It requires only information on the age and sex structure of the population. No data on births are needed • Extremely crude measure but if fertility is high, the child/woman ratio will be high, while the fertility is low, the ratio will be low • This is not a good measure to compare populations with substantially different levels of infant and child mortality, or where underreporting of young children is a problem

Crude Birth Rate (CBR) The number of live births per 1000 population in a

Crude Birth Rate (CBR) The number of live births per 1000 population in a specified area at a specified year B CBR = -------- X 1000 P Where, B = the total number of live birth during the calendar year P = the total population at the middle of the year

Exercise : CBR • Use the following data to calculate the CBR per 1,

Exercise : CBR • Use the following data to calculate the CBR per 1, 000 Island of Mauritius, 1985 Total Births: 18, 247 Total female population: 491, 310 Total male population: 493, 900

Solution 18247 CBR = -------- X 1000 985210 =18. 5 births/1, 000 population Baby

Solution 18247 CBR = -------- X 1000 985210 =18. 5 births/1, 000 population Baby girls-5000 Male population female population baby boys 4800 220000 2300000

Crude Birth Rate (CBR) • Why ‘crude’? • It includes all ages and both

Crude Birth Rate (CBR) • Why ‘crude’? • It includes all ages and both sexes in the denominator • Does not take into account proportion in the population 'at risk’ of having birth • Ignores the population age structure • Not good for comparing fertility across populations, as variations in age distribution of the populations being compared will affect the birth rate

Crude Birth Rate (CBR) • Despite crudeness, often used because: • It is very

Crude Birth Rate (CBR) • Despite crudeness, often used because: • It is very easy to understand • Only requires two pieces of information population size and the number of births in that year

General Fertility Rate (GFR) The general fertility rate (also called the fertility rate) is

General Fertility Rate (GFR) The general fertility rate (also called the fertility rate) is the number of live births per 1000 women in child bearing age (15 -49) in a given year. B GFR = ---------- X 1000 P (15 -49) Where, B = the total number of live birth P (15 -49) = the number of women of child bearing age (15 -49)

Exercise: GFR • Use the following data to calculate the GFR per 1, 000

Exercise: GFR • Use the following data to calculate the GFR per 1, 000 women aged 15– 49 Age No of women (000) No of live births 15 -19 20 -24 25 -29 30 -34 35 -39 40 -44 45 -49 20 18 14 8 6 4 3 160 1200 800 46 35 10 5 Total 73 2256

Solution B GFR = ---------- X 1000 P (15 -49) 2256 =---------- X 1000

Solution B GFR = ---------- X 1000 P (15 -49) 2256 =---------- X 1000 73000 = 30. 9/1000 women

GFR: advantage and limitations • More refined measure than CBR to compare fertility across

GFR: advantage and limitations • More refined measure than CBR to compare fertility across populations • But Need more data to calculate GFR than CBR • Require age composition of the female population • Comparisons using GFR is misleading because births are not spread evenly over the reproductive age range To overcome this need another measure that will consider fertility rates for each group

General marital fertility rate (GMFR) It is defined as number of live birth per

General marital fertility rate (GMFR) It is defined as number of live birth per 1000 married women of child bearing age in a given year. Total number of live birth GMFR = -------------------X 1000 Mid year population of married women of child bearing age

Age specific fertility rate (ASFR) It is defined as number of births per 1000

Age specific fertility rate (ASFR) It is defined as number of births per 1000 women of the specified age group. Bi ASFR = ------- X 1000 Pi Where, Bi = the number of live births to women of the specified age interval (usually 5 years) Pi = the number of women of the specified age interval

Exercise: (ASFR) Use the following data calculate the ASFR Age No of women (000)

Exercise: (ASFR) Use the following data calculate the ASFR Age No of women (000) No of live births 15 -19 20 -24 25 -29 30 -34 35 -39 40 -44 20 18 14 8 6 4 160 1200 800 46 35 10 45 -49 3 5 Total 73 2256

Solution Age No of women (000) (1) 15 -19 20 No of live births

Solution Age No of women (000) (1) 15 -19 20 No of live births (2) 160 ASFR/1000 (2/1) 8. 0 20 -24 18 1200 66. 7 25 -29 14 800 57. 14 30 -34 8 46 5. 75 35 -39 6 35 5. 83 40 -44 4 10 2. 5 45 -49 3 5 1. 67 Total 73 2256 147. 59

Age specific fertility rate (ASFR): • The great inconvenience of ASFRs is that they

Age specific fertility rate (ASFR): • The great inconvenience of ASFRs is that they are not a single number but a set of at least 7. this makes comparisons complex and tedious - But this can be overcome by using the Total Fertility Rate (TFR)

Total Fertility Rate (TFR) TFR------combined ASFR for all ages – How many children women

Total Fertility Rate (TFR) TFR------combined ASFR for all ages – How many children women have had at the end of reproductive years – Best single measure to compare fertility across populations

Total Fertility Rate (TFR) TFR represents the average number of children a women (or

Total Fertility Rate (TFR) TFR represents the average number of children a women (or a group of women) would have if she were to pass through her reproductive years bearing children at the same rate as the women now each age group This measure given the approximate magnitude of completed family size.

Total Fertility Rate (TFR) It is calculated by adding up age specific fertility rate

Total Fertility Rate (TFR) It is calculated by adding up age specific fertility rate and multiplying the sum by 5 (as the age interval is 5 years). It is usually expressed as per women instead of per 1000 women. ASFR X 5 TFR = -------------1000

Exercise: TFR • Use the following data to calculate the TFR Age No of

Exercise: TFR • Use the following data to calculate the TFR Age No of women (000) No of live births 15 -19 20 -24 25 -29 30 -34 35 -39 40 -44 45 -49 20 18 14 8 6 4 3 160 1200 800 46 35 10 5 Total 73 2256

Solution Age No of women (000) (1) 15 -19 20 No of live births

Solution Age No of women (000) (1) 15 -19 20 No of live births (2) 160 ASFR/1000 (2/1) 8. 0 20 -24 18 1200 66. 7 25 -29 14 800 57. 14 30 -34 8 46 5. 75 35 -39 6 35 5. 83 40 -44 4 10 2. 5 45 -49 3 5 1. 67 Total 73 2256 147. 59

Solution ASFR X 5 TFR = -------------1000 147. 59 X 5 = -------------1000 =

Solution ASFR X 5 TFR = -------------1000 147. 59 X 5 = -------------1000 = 0. 737 child per woman

Total Fertility Rate (TFR) Advantage -A single figure measure. Easy to compare -Consider age

Total Fertility Rate (TFR) Advantage -A single figure measure. Easy to compare -Consider age structure (GFR partially and CBR not at all) Disadvantage -Requires a lot of data: births by age of mother and women by age group

Current fertility rates of Bangladesh Age-specific fertility rates per 1000 women, by residence, Bangladesh

Current fertility rates of Bangladesh Age-specific fertility rates per 1000 women, by residence, Bangladesh 2007 Age group 15 -19 20 -24 25 -29 30 -34 35 -39 40 -44 45 -49 Source: BDHS 2007 Residence Urban 90 161 123 66 31 7 0 Total Rural 137 177 126 173 129 71 35 11 1 127 70 34 10 1

Current fertility rates of Bangladesh Age group Residence Total Urban Rural TFR 2. 028

Current fertility rates of Bangladesh Age group Residence Total Urban Rural TFR 2. 028 (2019) 2. 8 2. 7/woman GFR 92 109 105/1000 women CBR 24. 7 26. 5 26. 1/1000 population Source: BDHS 2007

Trends in Total Fertility Rate of Bangladesh 1971 to 2007 Source: BDHS 2007

Trends in Total Fertility Rate of Bangladesh 1971 to 2007 Source: BDHS 2007

Reproduction Rates • Number of births in a population depends upon the number of

Reproduction Rates • Number of births in a population depends upon the number of women in reproductive age. The reproduction depends on the number of female children born. There are two incidence of reproduction. • Gross Reproduction Rate (GRR) • Net Reproduction Rate (NRR)

Gross Reproduction Rate (GRR) • This measure is very similar to the TFR except

Gross Reproduction Rate (GRR) • This measure is very similar to the TFR except that it considers only female births rather than all births • Gross reproduction rate is the average number of daughters that would born alive to a woman (or group of women), if they survive to the end of the reproductive period and if throughout their lives they are subjected to current ASFRs.

Formula B if GRR = 5 X ------- X k Pi Where, Bif =

Formula B if GRR = 5 X ------- X k Pi Where, Bif = number of live female birth registered during the year to mothers of age, where i is an interval of 5 years Pi= the number of women of the specified age interval k= 1000 or 1

Exercise: GRR Use the following data to calculate the GRR Age Female pop Pi

Exercise: GRR Use the following data to calculate the GRR Age Female pop Pi (1) No of female children born Bif (2) 15 -19 20, 000 4, 000 20 -24 40, 000 12, 000 25 -29 80, 000 32, 000 30 -34 60, 000 12, 000 35 -39 40, 000 16, 000 40 -44 20, 000 45 -49 4, 000 400 Total 2, 64, 000 80, 000

Exercise: GRR Use the following data to calculate the GRR Age Female pop Pi

Exercise: GRR Use the following data to calculate the GRR Age Female pop Pi 15 -19 (1) 20, 000 No of female children born Bif (2) 4, 000 Bif /Pi (2/1) 0. 2 20 -24 40, 000 12, 000 0. 3 25 -29 80, 000 32, 000 0. 4 30 -34 60, 000 12, 000 0. 2 35 -39 40, 000 16, 000 0. 4 40 -44 20, 000 4, 000 0. 2 45 -49 4, 000 400 0. 1 Total 2, 64, 000 80, 000 1. 8

Formula B if GRR = 5 X ------- X k Pi = 5 X

Formula B if GRR = 5 X ------- X k Pi = 5 X 1. 8 =9 per woman

 • Alternatively, if total number of female birth is known, GFR can be

• Alternatively, if total number of female birth is known, GFR can be calculated as follows, Total female births GRR = -------------- X TFR Total births

 • This assumption is satisfactory when one wants to compare levels of fertility

• This assumption is satisfactory when one wants to compare levels of fertility and/or gross reproduction across populations and over time. • But, for a more realistic assessment of the reproductive potential of a population, taking into account mortality, one needs to calculate the Net Reproduction Rate (NRR)

Net Reproduction Rate (NRR) • Average number of daughters that would be born to

Net Reproduction Rate (NRR) • Average number of daughters that would be born to a woman (or a group of women) if throughout their lives they are subject to current age-specific fertility and mortality rates

Calculating NRR Bf Bx Lx NRR= ---- ∑ ----- X ----Bt Px lo Bf

Calculating NRR Bf Bx Lx NRR= ---- ∑ ----- X ----Bt Px lo Bf ---= Proportion of total births that are female Bt Bx ---= Age specific fertility rate at age x and Px Lx ---= is a life table survival rate with lo being the radix of lo the life table or 100000

Another method of calculating NRR Number of girls survived after their mortality experience NRR=-----------------------------Number

Another method of calculating NRR Number of girls survived after their mortality experience NRR=-----------------------------Number of cohort women survived at their end of reproductive period as per their mortality experience

Net Reproduction Rate: Relationship with GRR and TFR • NRR is always lower than

Net Reproduction Rate: Relationship with GRR and TFR • NRR is always lower than GRR, because it takes into account the fact that some women will die before entering and completing their child-bearing years • Correspondingly NRR will be less than half the magnitude of the TFR

Replacement Fertility • Replacement-level fertility is the level of fertility at which women in

Replacement Fertility • Replacement-level fertility is the level of fertility at which women in the same cohort have exactly enough daughters (on average) to “replace” themselves in the population. An NRR of 1. 00 is equal to replacement level • Once replacement-level fertility has been reached, births will gradually reach equilibrium with deaths, and in the absence of immigration and emigration, a population ultimately will stop growing and become stationary. The time this process takes varies greatly depending upon the age structure of the population

Replacement Fertility • The TFR can also be used to indicate replacement-level fertility by

Replacement Fertility • The TFR can also be used to indicate replacement-level fertility by showing the average number of children sufficient to replace both parents in the population. In the developed countries today, a TFR of about 2. 1 is considered to be replacement-level. • Replacement level TFRs higher than exactly 2. 0 (one child for each parent) are needed because there are slightly more males than females born and not all females survive to their childbearing years. In developing countries with much higher mortality rates, TFRs higher than 2. 1 are necessary to achieve replacement level.

Assignment • Topic: Demographic characteristics of COVID-19 Pandemic in Bangladesh – Background • Global

Assignment • Topic: Demographic characteristics of COVID-19 Pandemic in Bangladesh – Background • Global burden and scenario • South Asian burden and scenario • Bangladesh burden and scenario – Updated data and explanation • Morbidity • Severity & Morality • Moderate & asymptomatic – – – Government response and initiatives Population awareness and response Key challenges to address the issues Recommendation for prevention as a public health professional Conclusions *In between 1600 -2400 words