"Rural-urban migration has been modeled by both demographers and economists since the 1960s. Little regard has been given by either discipline for the other's models.... The purpose of this paper is to address this void in the African context. We examine three hypotheses: (1) that variables explaining the net urban in-migration rates vary with the age of the migrants; (2) that changes in the availability of services in urban areas [are] a factor in migration; and (3) that cohort structures (age pyramids) are also part of the explanation."