Geo-additive models of Childhood Undernutrition in three Sub-Saharan African Countries

We investigate the geographical and socioeconomic determinants of
childhood undernutrition in Malawi, Tanzania and Zambia, three
neighboring countries in Southern Africa using the 1992 Demographic
and Health Surveys. We estimate models of undernutrition jointly
for the three countries to explore regional patterns of
undernutrition that transcend boundaries, while allowing for
country-specific interactions. We use semiparametric models to
flexibly model the effects of selected so-cioeconomic covariates
and spatial effects. Our spatial analysis is based on a flexible
geo-additive model using the district as the geographic unit of
anal-ysis, which allows to separate smooth structured spatial
effects from random effect. Inference is fully Bayesian and uses
recent Markov chain Monte Carlo techniques. While the socioeconomic
determinants generally confirm what is known in the literature, we
find distinct residual spatial patterns that are not explained by
the socioeconomic determinants. In particular, there appears to be
a belt run-ning from Southern Tanzania to Northeastern Zambia which
exhibits much worse undernutrition, even after controlling for
socioeconomic effects. These effects do transcend borders between
the countries, but to a varying degree. These findings have
important implications for targeting policy as well as the search
for left-out variables that might account for these residual
spatial patterns.