Study comparing 288 pairs of contiguous U.S. counties with minimum wage differentials from 1990 to 2006. Based on this, researchers found “no adverse employment effects” from a minimum wage increase. Source: Dube, Andrajit; Lester, T. William; Reich, Michael; "Minimum Wage Effects Across State Borders: Estimates Using Contiguous Counties", Working Paper Series, Institute for Research on Labor and Employment, 30 November 2010.