Multivariate analysis 13*

The analysis in this section is based on intervals that were begun in the 10 years ending

two years before the survey: 1968 - 1978 in GFS and 1977-1987 in GDHS. The

resultant set of intervals is intended to minimize selection bias. In addition, the series

provided is long enough to allow examination of trends and the sample size large

enough to permit stable estimates of coefficients (see Bumpass et al., 1986). The

analysis covers the second to the sixth birth intervals. The first birth interval was

examined in Chapter 5. Intervals for births of very high orders are excluded because

they are highly biased towards intervals that were begun close to the time of the survey.

The independent variables considered show significant effects for different birth

intervals. The results for the GFS show that all the five intervals initiated in the six

years before the survey are less likely to be closed shortly than those that have been

initiated 7- 11 years before the survey. The data also show that while ethnicity appears

to be significantly related to the pace of closing the second and the fourth birth

intervals, religion is significantly associated with only the sixth.

Also, place of

residence and age at initiation of the interval are marginally significant for the fifth

birth interval while years of education is associated with the fourth. The period effect

is quite similar for the GDHS too, except for the second birth interval for which the

differential is not statistically significant. Another finding is the reduced impact of the

period effect for all the intervals relative to that found in the GFS. As with the GFS

data, different covariates are marginally related to different birth intervals.

For

example, ethnicity is associated with the second, fourth and fifth intervals; years of

education for the second and fourth intervals; while age is associated with the sixth

interval.

Table 6.4.3 gives estimates of relative risks for the second to the sixth intervals pooled

together within each survey. The data indicate that there is no difference in the risk of

having the second to the sixth births for religious and place of residence groups in both

surveys. In the GFS, the risk of closing the second to the sixth birth net of the effect of

education and period, is significantly lower for the Ewe and the Mole-Dagbani than for

the Akan group. For example, the Ewes have about 16 per cent while the Mole-

Dagbani have about 22 per cent lower risk than the Akans. However, in the GDHS,

only the Mole-Dagbani are significantly different from the Akans with about 28 per

cent lower risk.

Table 6.4.3 Estimated regression co-efficient from discrete time Cox proportional hazard model:

S u r v e y s GFS G D HS RR Z -stat RR Z -stat Covariates Ethnicity A kan 1 1 G a-A dangbe 1.017 -0.257 .997 -0.038 Ew e 0.838 -3.222 .936 -1.167 M ole-D agbani Education 0.778 -5.025 .724 -4.687 N one 1 1 1-10 years 0.884 -3 .0 7 4 .934 -1.493 11 + years Period 0.920 -.820 .736 -3.096 1 st 5 years 1 1 2nd 5 years 0.483 19.50 .743 -7.26

The effect of education on child-spacing is as expected in the GDHS. The relative risk

of having a birth shortly after the previous one is inversely related to the years of the

woman's education but the difference in the risk is only significant for women with

higher education. The GFS appears to show a curvilinear relationship with women

having no education and those having higher education being more likely to have

subsequent births soon after a previous birth compared to women having up to ten

years of education. A similar finding about the effect of education for fertility was

reported by Shah and Singh (1985) and was noted in Chapter 1.

Education is generally negatively associated with fertility. Cochrane et al. (1980)

mentioned three mechanisms by which higher educational achievement may result in

lower fertility. They noted that higher education is mostly associated with later age at

marriage which in turn leads to lower fertility. Also, more educated women tend to be

more efficient users of modem contraception, and finally education acts to change the

focus of women with respect to desired family size through changes in value systems.

This negative association appears to be true in the Ghanaian situation for the more

recent data in this analysis. This suggests that more female education, if encouraged,

can become a promising path to lower fertility in Ghana.

The period variable seems to be the most important one, influencing child-spacing net

of the effect of ethnicity and education in the 11 years preceding either survey although

its impact appeared to have lessened considerably in the GDHS. For example intervals

initiated in the six years before the GFS have about 52 per cent lower risk of being

closed early compared to those started 7 - 1 1 years before the survey. The intervals in

the six years before the GDHS have only 26 per cent lower risk of being closed shortly

after their inception.

6.12 Conclusion

This chapter presented various analyses of the birth interval data in the GFS and GDHS

data. One main objective was to compare the distributions of the lengths of the

intervals obtained in the two surveys. The analysis also sought to determine whether

the average birth interval length has been increasing over time and whether selected

background variables influence the time taken to close specific intervals. One finding

is that the average length of intervals actually closed by year of closure appears to be

increasing with time. While this may represent a genuine trend, it could also be an

artefact of the data.

The distributions of the time to closing the second to the sixth birth intervals are

generally similar in both surveys. The risk of closing these intervals is either the same

or slightly lower in the GDHS. The evidence in Table 6.1 shows that the differences in

the length of birth intervals for the younger age groups are only marginally different

between the two surveys. Finally, there is some evidence of differentials for period,

ethnic and education categories. These findings suggest that there is some increase in

child spacing in Ghana although it does not appear to be a substantial change.