Abstract
This study focuses on the specification of distance and space in models of state-to-state population migration. Typically, space is captured by one or two simple variables that do not adequately model the spatial relationship between states. These are particularly poor measures for states with a common border, especially those with a metropolitan area located near the border. Four models of interstate population migration are developed, with increasingly complex specifications of space. The models are estimated using 1975 to 1980 migration data for the 48 contiguous states of the United States. Common borders and bordering metropolitan areas do influence interstate population flows. Models lacking a more detailed specification of space will lose explanatory power and suffer from biases.