Analysis of the determinants of net migration rates, comparing persons under age 65 with those over age 65, for nonmetropolitan areas over three time periods (1950–60, 1960–70, 1970–75) supports the following conclusions: (1) economic factors are more important determinants of migration for the young than for the elderly; (2) the reverse is the case for noneconomic factors; (3) over time, the influence of economic determinants diminishes for the young and the elderly; (4) noneconomic determinants are gaining in importance for both populations; and (5) temporal change in the relative importance of both economic and noneconomic factors is most evident in the younger population. These conclusions support the ecological proposition that migration is an adaptive response to organization change. Findings also imply that we must look beyond the community context to broader societal change in order to explain changing migration patterns in nonmetropolitan areas.