Functional forms and the relevance of contiguous migration in the study of migration and employment growth

Previous studies on interstate migration have dealt with total migration without decomposing it into contiguous and noncontiguous migration flows. Since migration over borders of contiguous states may merely reflect changes in residence without changes in economic activities, the use of total migration data might reduce the reliability of empirical results. In this study, a simultaneous-equation model containing two equations, one for migration and the other for employment growth, has been specified in a general form and estimated by the 2SLS method for total, contiguous and noncontiguous migration flows. Results obtained from the use of 1970 Census data show that noncontiguous migration behaves significantly different from contiguous migration, and that noncontiguous migration, rather than total migration, should be used for the study of factors affecting interstate migration. Results also indicate that the log-linear functional form commonly used in empirical studies cannot be accepted statistically.