Ran Abramitzky and colleagues studied the impact of immigration restrictions in the 1920s on the labor market in the United States and found that they caused an influx of rural people into cities. How did farmers compensate for the loss of workers? They switched to capital-intensive farming - in other words, they mechanized it. This was the case in the 1920s, but what about today? It is highly likely that dependence on migrant labor discourages automation.