DECOMPOSITION ON ANALYSIS OF DETERMINANTS AND CHANGE IN FERTILITY IN NIGERIA: 2003-2013

ABSTRACT

Introduction: High fertility has now been identified as threat to public health because of its negative effect on maternal and child health. Globally, human population is increasing at an average rate of 1.1% per year and it has been predicted that it will be about 9.6 billion by year 2050 (Debebe, Limenih, and Biadgo 2017). In Nigeria, high population growth rate has been identified in many studies as one of the major causes of maternal and child mortality. Several multivariate techniques had been employed in assessing the effects of various fertility determinants on fertility level in Nigeria but very few had considered the use of decomposition method. Thus, the main purpose of this research is to estimate the contribution of each of the selected determinants of fertility to the gap in fertility decline between 2003 and 2013 using Oaxaca Decomposition method.

Method:

The study focused on women of reproductive age. The percentage of each determinant of fertility like age of women at the year of survey, residence (urban or rural), marital status, highest education level, religion, wealth index, age at first birth, contraceptive use, fertility preference and sex preference was measured from each survey year to estimate their contribution to the TFR of that year. Descriptive statistics like percentage, mean fertility, percentage change in mean fertility were carried out. The Blinder Oaxaca decomposition model was used to check the contribution of each of the determinants to fertility in each year. Negative binomial regression was used to identify the determinants of fertility for each year (𝛼 = 5%).

Results:

The study findings showed that the mean age of the women and children ever born in 2003, 2008 and 2013 respectively was (35.64±8.125, 35.56±8.149, 35.89±8.092) and (6.37±2.929, 6.16±2.901, 6.06±2.846). The decomposition analysis showed that age of women (23.5%, 24.4% and 23.2% respectively), marital status (132.4%, 97.6% and 91.9% respectively), religion (31.4%, 46.8% and 54.1% respectively), fertility preference (50.7%, 57% and 67.4% respectively) and the type of residence (12.7%, 12.8% and 5.6 % respectively ) significantly contributed to rise in fertility. While Age at first birth of women (28%, 25.3% and 23.2% respectively), education (15.9%, 13.7% and 15.5% respectively), child sex preference (26.6%, 16.7% and 34.6% respectively) and wealth index (17.4%, 23.7% and 28.1% respectively) significantly contributed to reduction in fertility. Mean fertility was 4.04 (C.I = 3.28 – 4.96), 3.22 (C.I = 2.96 – 3.51) and 3.34 (C.I = 3.09 – 3.61) respectively times higher in ever married than the never married women in 2003, 2008 and 2013. It was 0.84 (C.I = 0.77 – 0.92), 0.85 (C.I = 0.82 – 0.89) and 0.74 (C.I = 0.71 – 0.78) respectively times higher in Christians than other religions. It was 1.35 (C.I = 1.29 – 1.41), 1.36 (C.I = 1.34 – 1.39) and 1.52 (C.I = 1.49 – 1.55) respectively times higher in women with +5 fertility preference than in women with