Method and materials of estimating current fertility in Benighat

The own-children method (Cho, 1973) of fertility estimation and subsequent refinements in the method (Cho, et al., 1986) provides a useful tool for analysing patterns and trends in fertility in Benighat. EASWESPOP, a Software package program developed by East-West Center (1987) has been used to estimate current fertility for the study village.

The own-children method uses the relationship of mothers with their children. All children aged 0-14 years are matched with mothers aged 15-64 years who are living in the same household. All matched children are referred to as own-children and the remaining unmatched children are referred to as non-own-children. All such unmatched children are evenly distributed to mothers of matched children on the assumption that the age distribution of mothers of the unmatched children is the same as that of mothers of matched children.

The own-children method is a survey or census-based reverse survival technique for estimating age-specific fertility rates and all women aged 15-64 and children aged 0-14 are reverse survived for 15 years preceding the survey. Although the method provides age-specific fertility rate for each of the 15 years preceding the survey, in the present application, rates are calculated for each of the previous 2-13 years. This is done to minimize the effect of underenumeration of children aged 0 and 1, which if included in the estimates may give a spurious fertility decline during those two years (Retherford et al., 1979: 9). Similarly, estimates for the distant past (14 and 15 years before survey) have been disregarded because the estimates are based on a relatively small number of cases and this reduces sample variability. Schroeder and Retherford (1979) used this approach to estimate fertility from Nepalese village-study data. The method further assumes that appropriate life tables are available to the study population 15 years before the survey date

(Retherford et al. 1979; Cho, Retherford and Choe: 1986). The reliability of the method is enhanced if the following conditions are met: accurate age classification, low migration rates, clearly specified kin relationship, lower proportion of non own-children and low levels of mortality (Retherford et al., 1979: 4-9; Schroeder and Retherford, 1979: 248; Ogawa, 1980: 65-66).

Although there is a heavy preference for digits ending in 0, 5, and to a lesser extent to even numbers, the age reporting seemed to be improving in the study village. This is evident from the fact that the Myers summary index of digit preference was 6.3 (Chapter 2). Age heaping of children rather than of the mother is of more serious concern in the application of this method (Schroeder and Retherford, 1979; Retherford et al., 1979) and the events being more recent, children's ages are reported more accurately. Furthermore, quality of age data in this study will not be a serious problem as every effort was made to elicit the correct age of mother and children. Local enumerators were used and in cases where the age of a person was doubtful, further probing was done to find out the current age.

Based on the relationships with the head of the household, children below the age of 15 were matched with their own mothers. The proportion of children who could not be matched with their own mothers referred to as non-own-children, is only 3.3 per cent. Table 4.1 gives the distribution of number of women and children used for the application of the own-children method of fertility estimation for Benighat.

Migration may not pose a serious problem in this study as it is mostly seasonal and selective of male adults. The construction and operation of a highway connecting the village and intensification of horticultural and vegetable crops have created employment opportunities in the village, thereby reducing the need for permanent migration elsewhere.

Levels of mortality are not adequately known for the study population. Although a low mortality level is desirable it is not a serious problem, as it has been contended that the own-children method is fairly robust to errors in mortality estimation

(Schroeder and Retherford, 1979: 250). The Central Bureau of Statistics (1989) estimated a life expectancy at birth of 52.1 years for females for the year 1989. The national estimate of 52 years of life expectancy is assumed to hold for Benighat population and the Coale and Demeny Model West life tables have been used for generating reverse survival ratios.

Table 4.1: Number of women and children matched by age of women

A ge o f wom en N o o f wom en N o. o f ow n- children aged 0-14 15-19 58 25 20-24 118 206 25-29 144 375 30-34 110 360 35-39 105 282 40-44 80 175 45-54 104 90 55 + 48 1 Total 767 1514 N o o f non-own-children Total children Per cent o f unmatched children 51 1565 3.3

4.4 Results

Although the own-children method produces age-specific and total fertility rates from 1974 to 1988, for reasons discussed above, only rates for the past 2-13 years (based on children aged 2-12 years) from the survey are considered here (Table 4.2). To minimize the effect of age heaping on fertility estimates, rates based on 3-4 years moving averages are also presented in Table 4.2.

Table 4.2: Age-specific and total fertility rates for Benighat, 1976/79 to 1983/86 A ge Group 1976/79 Year 1980/82 1983/86 Per cent change (1976/79- 83/86) 15-19 223.8 231.5 231.1 +3.3 20-24 308.2 329.5 263.7 - 14.4 25-29 276.1 244.3 241.4 - 12.6 30-34 249.6 172.4 152.4 - 3 8 .9 35-39 167.4 157.1 133.7 -2 0 .1 40-44 52.4 21.4 35.0 - 3 3 .2 45 + 0.0 0.0 0.0 0.0 1277.5 1156.1 1057.3 Total Fertility Rate 6.4 5.8 5.3

Per cent change (between the period)

-9.0 -8.5 -17.2

Source: Benighat Survey, 1988

Table 4.2 shows that the age-specific and total fertility rates have declined in recent years. The fertility trends are also depicted in Figures 4.1-4.2. Between the periods 1976/79 and 1980/82, the total fertility rate declined by 9 per cent, from 6.4 to 5.8 children per woman. The total fertility rate showed a further decline of 8.5 per cent from 1980/82 to 1983/86, from 5.8 in 1980/82 to 5.3 in 1983/86.

Figure 4.1: Trends in Total Fertility Rate, Benighat, 1976-86

Moving Average

Source: Data calculated from Table 4.2.

Figure 4.2: Age-specific fertility rates for Benighat, 1976/78-83/86.

21 >.

I

1

cp 0> ÖO < Estimates for — -□— 1976/78 --- • — 1979/82 - - 0 - 1983/86 250 - 200 - 15-19 20-24 25-29 30-34 35-39 40-44 45 + Age Group Source: Table 4.2.

The age-specific fertility rates shown in Table 4.2 reveal a similar trend. However, the fertility of woman aged 15-19 years and 20-24 years seems to have increased slightly during the period 1976/79 to 1980/82. A slightly higher fertility of younger women can be attributed to the better nutritional standard brought about by the enhanced economic opportunities in the village. This is consistent with the findings of the Nepal Fertility and Family Planning Survey (FP/MCH, 1987).

This table also shows that there has been a shift in the age pattern of childbearing during the study period. In 1976/79, age-specific fertility of women aged 30-34 ranked third in its contribution to the TFR. In 1983/86, the 30-34 age group was replaced by the 15-19 age group to rank third to contribute to the TFR. The highest age-specific fertility rate, however, pertained to the 20-24 age group, followed by the 25-29 age group in all the periods.

Table 4.2 also shows that the largest decline in age-specific fertility occurred to women in the older age groups. The age-specific fertility rate during the period declined by 38.9 per cent for the 30-34 age group and 33.2 per cent for the 40-44 age group.

In document The socioeconomic context of high fertility in rural Nepal : the case of Benighat (Page 115-120)