July 2024 data for border crossings showed the lowest level of border crossing since September 2020. Between 2007 and 2018, visa overstays have accounted for a larger share of the growth in the illegal immigrant population than illegal border crossings, which have declined considerably from 2000 to 2018. In 2022, only 37% of illegal immigrants were from Mexico, the smallest share on record. El Salvador, India, Guatemala and Honduras were the next four largest countries. As of 2016, approximately two-thirds of illegal adult immigrants had lived in the US for at least a decade. As of 2022, unauthorized immigrants made up 3.3% of the US population, though nearly one-third of those immigrants have temporary permission to be in the United States, such as those in Deferred Action for Childhood Arrivals.

Opponents of illegal immigration worry about crime, as well as possible social and economic burdens caused by migration. Opponents also insist immigrants enter the United States through a formal process and do not want to reward those bypassing the system.

Research shows that illegal immigrants increase the size of the US 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 illegal immigrant population would increase the immigrants’ earnings and consumption considerably, and increase US gross domestic product. Most scientific studies have shown that illegal immigrants commit less crime than natives and legal immigrants. Sanctuary cities—which adopt policies designed to avoid prosecuting people solely for being in the country illegally—have no statistically meaningful impact on crime. Research suggests that immigration enforcement has no impact on crime rates.