This paper tests the relationship between primacy and economic development for countries in Asia and the Americas. It tests explanations for primacy drawn from several social-science disciplines--demography, economics, geography, political science, and sociology. The study is one of the first to use panel-data estimators for the tests. Economic and domestic political variables are found to be important determinants of primacy. In particular, rent-seeking and dictatorial governments are associated with primacy, but the association exists independent of the level of economic development. The implication from dependency and world-system theories that current international economic interactions promote primacy is not supported. It also examines the hypothesis that primacy first increases and then decreases with GDP per capita.