New Evidence that Making Legal Migration Easier Reduces Illegal Border Crossings

Economist Michael Clemens has the most extensive and sophisticated analysis of this issue to date.

(Miguel Juarez Lugo/ZUMAPRESS/Newscom)

I and others have long argued that making legal migration easier is the best way to reduce disorder at the border. To a large extent, this basic Economics 101: if a much-coveted good or service is banned or severely restricted, that predictably creates a large black market. Thus, just as alcohol prohibition led to widespread bootlegging and illegal purchases from the likes of Al Capone, so severe migration restrictions predictably incentivize illegal migration. In a new paper for the Peterson Institute for International Economics, my George Mason University colleague Michael Clemens—one of the world's leading immigration economists—provides the most extensive and sophisticated analysis of this issue to date.

Here is the abstract, summarizing his findings:

An increasing number of migrants attempt to cross the US Southwest border without obtaining a visa or any other prior authorization. 2.5 million migrants did so in 2023. In recent years, responding to this influx, US officials have expanded lawful channels for a limited number of these migrants to cross the border, but only at official ports of entry. These expanded lawful channels were intended to divert migrants away from crossing between ports of entry, by foot or across rivers, thereby reducing unlawful crossings. On the other hand, some have argued that expanding lawful entry would encourage more migrants to cross unlawfully. This study seeks to shed light on that debate by assessing the net effect of lawful channels on unlawful crossings. It considers almost 11 million migrants (men, women, and children) encountered at the border crossing the border without prior permission or authorization. Using statistical methods designed to distinguish causation from simple correlation, it finds that a policy of expanding lawful channels to cross the border by 10 percent in a given month causes a net reduction of about 3 percent in unlawful crossings several months later. Fluctuations in the constraints on lawful crossings can explain roughly 9 percent of the month-to-month variation in unlawful crossings. The data thus suggest that policies expanding access to lawful crossing can serve as a partial but substantial deterrent to unlawful crossing and that expanding access can serve as an important tool for more secure and regulated borders.

This is a large effect. It implies, for example, that doubling the number of people allowed to cross the border legally would reduce illegal entry by %30. At the same time, we should not be surprise that the effect falls short of a 1 to 1 correspondence. For obvious reasons, many new legal entrants won't necessarily be people who would otherwise have tried to enter illegally.

I would add that, while Clemens uses an extensive body of data, none of the measures easing legal entry came anywhere close to legalizing it for a large majority of those seeking to immigrate into the United States. Even at its most permissive, border policy during the period studied still barred legal entry to the large majority of would-be migrants.

A more extensive shift towards "open borders"—such as allowing entry to anyone who registers with the authorities and there is no evidence he or she plans to engage in crime or espionage—might well lead to the near-total cessation of illegal migration, thereby also eliminating all or most involvement by organized crime. Similarly, the end of alcohol prohibition largely eliminated the role of organized crime in that industry.

Obviously, preventing disorder at the border is far from the only rationale for immigration restrictions. If your main reason for advocating restrictionism is some other rationale, such as preventing immigrants from overburdening the welfare state or spreading potentially harmful cultural values, Clemens' results may not move you much. I address many of these other types of concerns in detail in Chapters 5 and 6 of  my book Free to Move: Foot Voting, Migration, and Political Freedom. But "border security" has become a major rationale for restrictionism in public debate, one that often gets more attention than any other. Clemens' important work adds to the already considerable evidence indicating that we can effectively address that issue by making legal migration easier.

In a previous post, I wrote about Clemens' new paper showing that mass deportations of migrants destroy more jobs for native-born Americans than they create. His most famous article describes the enormous economic benefits of dropping immigration restrictions, which could well result in a doubling of world GDP.