Joint distribution of child mortality and wealth across 30 sub-Saharan African countries over 2000-2019

Abstract

Background: While reductions in child mortality have been observed across sub-Saharan African countries in the last 30 years, narrowing the gaps in under-five mortality across socioeconomic groups also requires an understanding of the multiple associations between health and welfare and socioeconomic drivers. We examined the probability density distributions in under-five mortality within countries and joint pathways of under-five mortality and wealth over time.

Methods: We used 69 Demographic and Health Surveys and 19 Malaria Indicator Surveys from 30 sub-Saharan African countries, with each country having at least two surveys conducted since 2000. We constructed a cross-country wealth index and estimated under-five death prevalence. We examined the pure distribution in under-five mortality prevalence and the joint probability distribution of wealth and under-five mortality prevalence over time, including the area of confidence ellipse which spanned the two dimensions of mortality and wealth and covered 75% of the mass of the joint distribution.

Results: Most countries experienced decreases in under-five mortality along with increases in wealth over time. However, we observed great variations in the evolution of the joint distributions across countries over time. For instance, the areas of confidence ellipse ranged from 0.178 in Ethiopia (2000) to 1.119 in Angola (2006). The change (over time) in the area of confidence ellipses ranged from 0.010 in Tanzania to 0.844 in Angola between the 2000s and 2010s. The ranking of country performance on under-five mortality varied greatly, depending on whether performance summary indicators were based on disaggregation by wealth or on full non-disaggregated distributions.

Conclusions: Our analysis points to the relevance of full distributions of health and joint distributions of health and wealth as complementary indicators of distributions of health across socioeconomic status, in assessing country performance on health.

Figure 1

Probability density (full) distribution of under-five death prevalence (per 1000), 2004-2019, for six sub-Saharan African countries. Panel A: Angola. Panel B: Ethiopia. Panel C: Nigeria, Panel D: Senegal. Panel E: Tanzania. Panel F: Zimbabwe.

Figure 2

Evolution of the extent of under-five death prevalence (per 1000) across the 10th to 90th percentiles of the probability density (full) distribution of under-five death prevalence, across all country-years.

Figure 3

Joint probability density distribution of under-five death prevalence and wealth, 2004-2019, for six sub-Saharan African countries: Angola (2006, 2011, 2016), Ethiopia (2005, 2011, 2016), Nigeria (2003, 2010, 2018), Senegal (2005, 2012, 2019), Tanzania (2004, 2010, 2017), Zimbabwe (2005, 2010, 2015). The x-axis indicates the wealth category which varies from 1 (poorest) to 5 (richest). We calculated the wealth scores per country and per year using standardized measurements to allow comparisons across country-years and divided all country-years by five wealth categories equally. The y-axis indicates the category for the under-five death prevalence: the number of children who died at or before age five divided by the total number of children under age five multiplied by 1000/25 (division by 25 is used for scaling purposes).

Figure 4

Ranking (across all country-years, since 2000 for 30 sub-Saharan African countries) in different summary indicators of distribution in under-five death prevalence. Each column indicates the ranking of the country-years based on the following summary indicators. Column 1: difference in under-five death prevalence between 90^th and 10^th percentiles. Column 2: ratio of under-five death prevalence in 90^th percentile divided by under-five death prevalence in 10^th percentile. Column 3: difference in under-five death prevalence between wealth quintiles 1 and 5. Column 4: ratio of under-five death prevalence in wealth quintile 1 divided by wealth quintile 5.