Ethnic expansions and between-group differences in children's health: a case study from the Rukwa Valley, Tanzania.

The Sukuma ethnic group appears to be expanding across Tanzania at a rate far greater than other ethnic groups in the area. In this paper, the household-level dynamics that may be fueling this expansion are explored by comparing measures of infant mortality and child health with another Tanzanian ethnic group, the Pimbwe. Consistent with expectations, the Sukuma appear to have comparable levels of fertility but lower child mortality. As predicted, compared to the Pimbwe, Sukuma children are also heavier and taller for their age, suggesting better nutritional status. Four hypotheses about why the Sukuma are so successful in this area are addressed. Surprisingly, the results show that household food security and wealth are not related to children's nutritional status, nor can maternal effects account for the observed health differences. Several lines of evidence suggest that different patterns of infant feeding practices may underlie the differences in children's nutritional status.