The economic impact of undocumented immigrants in the United States is challenging to measure, and politically contentious. Research shows that undocumented immigrants increase the size of the U.S. economy/contribute to economic growth, enhance the welfare of natives, contribute more in tax revenue than they collect, reduce American firms' incentives to offshore jobs and import foreign-produced goods, and benefit consumers by reducing the prices of goods and services. Economists estimate that legalization of the undocumented immigrant population would increase the immigrants' earnings and consumption considerably, and increase U.S. gross domestic product.