Borders Behind the Border: An Exploration of State-Level Differences in Migration Control and their Effects on US Migration Patterns

Governments at various levels of administration increasingly try to exclude unauthorised migrants from labour markets and public provisions, and apprehend and deport unauthorised migrants who have settled in the territory. This article demonstrates that such policies and practices of 'internal border control' can be approximated empirically; it is shown that, since 2005 in particular, internal border control has become more prevalent in the United States, especially in Southern states. Furthermore, evidence is presented for a negative bivariate relationship between the degree of internal border control and the estimated rate of growth of unauthorised residence; states with the highest degree of interior control tended to experience the largest decreases in the size of the unauthorised population. We introduce four plausible interpretations of this bivariate relationship, and suggest various avenues for further research. The results are based on a primary analysis of three indicators of internal control (employer participation in E-Verify, restrictive state laws, county and city involvement in the 287g Program) and a secondary analysis of unauthorised population estimates.