Definition:- The term fertility denotes the state or condition of being fertile. The ability to conceive children is fertility. Fertility is the natural capability to produce offspring. In demography, fertility refers to the occurrence of birth. Fertility is one of the three fundamental components of population growth, the others being mortality and migration of the population.
According to Thompson and Leirs (1976), “Fertility is generally used to indicate the actual reproductive performance of a woman or group of women”.
According to J. I Clarke (1972) “ Fertility is the occurrence of live birth and must not be confused with fecundity by which we normally mean reproductive capacity or the ability to have children. Fertility can be measured, but Fecundity can not be.
Measurement of Fertility: - Reference time and lie birth are important for fertility measurement.
Live Birth:- A live birth is any infant who breathes or shows any other evidence of life ( Such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles ) after separation from the mother’s uterus, regardless of the duration of gestation. Each product of such a birth is considered live-born.
Various measures of fertility have been coined. Following are the important measures of fertility ----
Crude Birth Rate ( CBR ), General Fertility Rate ( GFR ), Age-Specific Fertility Rate (ASFR ), Total Fertility Rate ( TFR )
(1) CRUDE BIRTH RATE ( CBR ):-It is one of the most commonly used measures for fertility. It is expressed in terms of the number of live birth in a year per thousand mid-year population. It may be pointed out that only live births during a year are to be taken into account.
FORMULA:– CBR = B/P ×k, Where, B = Number Of live birth in a calendar year in a given geographical area. P = Mid-year total population of the same calendar year of the same geographical area.
K = Constant, Usually 1000
Calculation = 163/9281 ×1000 = 17.56 = 18
Interpretation:- CBR 17.56 refers to that there is around 18 live birth per 1000 population. CBR Usually ranges ( 5 – 6 ) to ( 50 - 55).
A CBR of 5-10 refers to one of the lowest levels of CBR. Maximum CBR can go 50-55, It refers to very critical conditions that may occur in a population explosion.
Positive side:- i) It is easy to calculate ii) It is simple to understand and easier to collect data from the field. iii) It is widely used among demographers planners, and Population studies.
Problem:- Crude automatically refers there has the same problem in the formula. Crude means something gross that gives the scope for improvement i) In this formula numerator is already included in the denominator. ii)In the childbearing process, the woman is playing the main role, but where the total population is taken into consideration. iii) Probability of childbearing is much more at the age of 20-30.
(2)GENERAL FERTILITY RATE:- It is important over CBR. Therefore it takes into account only the female population in the child-bearing age groups. It measures the number of live births in a year per thousand women of a normal reproductive age.
FORMULA:- GFR=Number of live birth in a calendar year in a given geographical area / mid-year female population of that calendar year and that geographical area aged(1545/49) x K
Calculation=(163/1882)x 1000=86.60=87
Interpretation:- GFR 86.60 refers that there is around 87 live birth per 1000 woman population in the age group of (15-45)/49 Problem:- i) This formula includes every woman who is eligible or non-eligible to give birth to a child. In particular age groups say in 20-29 the childbearing rate is considerably higher than in the 15-19 and 30-44 age groups and thus there is only partial standardization for age.
(3) AGE-SPECIFIC FERTILITY RATE:- Age-specific fertility rate has been considered a more useful index of fertility. It measures the number of live births in a year to women of a given age group per 1000 women in that age group.
FORMULA:-ASFR =Number of live birth in a calendar year in the well-defined geographical area/ Mid-year female population of that calendar year and that geographical area aged (1545/49)X 1000
ASFR = 10/360×1000 = 27.77
Interpretation:- These are the (say) 27.77, 147.28, 145.83, 96.86, 38.91, and 10.47 ASFR of various age groups. These are 27 number of birth at the age group of 15-19.
Problem:- If we compare the ASFR of the different countries it is not possible to count every age group and compare the ASFR. So, we have to go through the next process TFR.
(4)TOTAL FERTILITY RATE (TFR):- The total fertility rate is another measure of fertility, Which has been regarded as the most sensitive and most meaningful measure of fertility. It is obtained by summing up the age-specific birth rate and multiplying it by the number of years in age interval.
FORMULA:-TFR = Summarization of all birth that took place in the woman age group say 15−19 to 40−44 /1000× I Where i = interval
Calculation = ∑4015−−1944/100 ×i
= 467.12/1000 × 5
= 2.33
calculation:-
Interpretation:- If a woman surpasses her all-childbearing process. She is expected to deliver 2.34 babies/live birth
Positive side:- Total fertility rate is easy to compute and is an effective measure of fertility.
The others measure of fertility are:-
GROSS REPRODUCTION RATE (GRR):-
FORMULA :-GRR = Fb/Fr×1000
Where Fb = Total births of female babies. Fr = Total number of females in the reproduction age group
Net Reproduction Rate (NRR), Age-Specific Marital Fertility Rate (ASMFR), Child women ratio.
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