2020, Paper, "For most of America’s history, migrants have moved in large numbers from less productive places to more productive places. For the past 150 years, the movement to the urban frontier has been distinctly more economically important than movement to areas with little human settlement. Over the past 50 years, migration to America’s most productive cities has been increasingly checked by the regulation of new construction. The closing of the urban frontier is associated with unaffordable housing, widening gaps in housing wealth, a spatial mismatch between local productivity, population growth, and the end of regional income convergence. One policy response to the change is to encourage state legislatures to take more regulatory power over construction or to provide localities with stronger financial incentives to build. Federal highway funding could be tied to the level of construction in high-demand areas. A second response is to accept the closed urban frontier and to embrace place-based policies that reduce joblessness in depressed areas through employment subsidies, social insurance reform, and experimental vocational training program."