Migrants cross through a gap in the US-Mexico border fence in Jacumba Hot Springs, California. Picture taken December 22, 2023.

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Offering more lawful pathways for US border crossings reduces unlawful crossings


Photo Credit: Qian Weizhong/VCG


The US debate over the historically unprecedented influx of immigrants at the southwest border has been at the center of the presidential campaign, producing anguished reactions across the spectrum. But the furor about how to change policy at the border has not always been informed by enough facts and understanding of the genuine dilemmas faced by policymakers.

On the one hand, a vast enforcement crackdown is likely to harm economic opportunity in the United States, where immigrants fill essential roles in the hottest job market in a half century. On the other hand, Americans cannot abide continuing chaos, especially in the border states and in some northern cities. Four out of five Americans are dissatisfied with the current policy. On both the political left and right, most voters see this disorder as a serious problem or even crisis

A rational way out of this crisis would be to set up a system expanding legal access for immigrants to the United States while retaining some categories as unlawful. In fact, as documented in my new study of how migrants at the border have responded to past changes in policy, the evidence shows that a system of expanding legal access would reduce illegal immigration.

Here are some basic facts: Last year 2.5 million migrants crossed the border without a visa or other prior authorization needed to prevent them from being deported—an all-time record. Some cross the border unlawfully, attempting to bypass border agents; others cross lawfully at official ports of entry. Many are quickly deported, because whether or not they crossed the border lawfully, they arrived without prior permission to stay and no exception is granted.

Others, such as parolees and asylum seekers, are given on-the-spot temporary relief from deportation by frontline Department of Homeland Security officials who have that discretion under law. This relief is given for various reasons: Officials might believe the migrant could win an asylum claim, the migrant’s origin country may not allow deportations, detention facilities might be unavailable, or other reasons. In other words, somepeople crossing the border without prior authorization do cross lawfully (at a port of entry) and are allowed to remain by federal officials exercising their legal authority. Such migrants, in the common usage of the word, entered and remain lawfully. (In legalese, their presence is “under the color of law.”)

Alleviating the border pressure by opening more channels for lawful migration is a strategy that was initially adopted by President Joseph R. Biden Jr.’s administration. In the abstract, this idea is supported by 56 percent of the public, and the administration has greatly expanded lawful permission for migrants arriving at the border to enter and remain. But critics of this policy  argue vehemently that expanded lawful migration acts as an incentive that “pulls” more people to the border. The perverse consequence could be to actually raise unlawful crossings, these critics contend.

This debate urgently needs evidence. In a crisis, sound policy comes not from partisan acrimony but from facts and experience, though of course some critics would in the end oppose any increases in immigration, whether legal or illegal.

I have just released a study bringing first-of-its-kind evidence to the table. I study the aggregate behavior of almost 11 million migrants encountered at the Southwest border—every man, woman, and child encountered there over the past 12 years without authorization to cross. On numerous past occasions, different administrations raised or lowered restrictions on the number of migrants who could cross lawfully at a port of entry and the fraction of those crossing lawfully allowed to stay. How did migrants respond?

The core finding of my analysis is that offering more lawful pathways to cross the border significantly decreases the rate of unlawful crossings, with this deterrent effect growing stronger over time. I find that a policy of increasing lawful entries by 10 percent leads to a 3 percent decrease in unlawful crossings after about 10 months. If those lawful channels do act as a “pull factor” bringing migrants to the border, it is not strong enough to result in a net increase in unlawful crossings. Policy that expands lawful crossings has tended to deter unlawful crossings.

The Method Behind the Analysis

To study the effect of lawful crossings on unlawful crossings, economists have to go beyond superficial correlations in the data. Moments of high generalized pressure on the border tend to push up both lawful and unlawful crossings but not necessarily because one causes the other. Asking whether lawful crossings cause unlawful crossings requires more sophisticated methods.

To dissect the intricate decision-making process of migrants, I employed a statistical tool called impulse-response functions. This method is very well established for distinguishing causation from mere correlation in economic data that change over time. The foundation of the method has yielded not one but two Nobel prizes.

Here’s how it works. Imagine we're studying the effects of a sudden increase in the availability of lawful border crossings (a policy "impulse") on the number of unlawful crossings (the "response"). A first approach might be to observe each month when there has been an uptick in lawful crossings and ask whether next month there is a rise or fall in unlawful crossings.

But that could lead you astray. A rise in lawful crossings in June, for example, could just arise from higher overall border pressure in May, which by simple inertia could lead to a rise in unlawful crossings that continues through July. So you could observe a positive relationship between lawful crossings this month (June) and unlawful crossings next month (July) even if one didn’t cause the other; both of them were caused by the rise in border pressure last month (May).

Impulse-response functions are built to cut away that thicket of problems. They ask: If we hold constant all the fluctuations in unlawful crossings over the past several months, and we hold constant all the fluctuations in lawful crossings over the past several months, then what happens when lawful crossings break from the past trend and rise? Do migrants respond by reducing unlawful crossings, or by coming to the border in such large numbers that unlawful crossings rise?

In the data I study from October 2011 through July 2023, the answer is clear. Migrants respond to increases in opportunities for lawful crossing by reducing unlawful crossings. In fact, 9 percent of all the variation in unlawful crossings during that 12-year period is explained by the variation in lawful crossings that government officials allowed. In limited but substantial measure, peaks in unlawful crossing are a product of policy.

Implications and Reflections

My study suggests that, contrary to a common belief that more accessible legal entry points might encourage unlawful migration, expanding lawful pathways could serve as one strategic tool—among many—in managing migration flows. This finding prompts a reconsideration of the role of legal entry options in the broader context of immigration control.

This study does not suggest that lawful channels can simply replace enforcement at the border. As I have written on many occasions, lawful channels and enforcement are better seen as complements—two necessary ingredients of the same recipe. Lawful channels increase the regulatory effectiveness of enforcement, and vice versa.

Beyond this, lawful channels for migration involve much more than simply decisions by border officials to allow or disallow crossings. They extend to work visas, family visas, asylum grants, refugee resettlement, and regularization programs. My study is not directly informative about every form of lawful channel. But it does move us forward on understanding the effects of an important form of policy change to better regulate chaos at the border.

Even under current law, there are numerous policy levers to increase lawful channels for crossing the border and for working in the United States. These include facilitating access to work visas for fundamental jobs, some of which have no numerical cap, and refugee resettlement. But the more important work lies in updating US law for modern needs. The basic framework of US law governing immigration was written by my great-grandparents’ generation. It has not had a serious reform in 34 years. Visionary reform efforts have included the substantial expansion of work visas for the express purpose of deterring unlawful migration, while fueling economic expansion and job creation in the United States. The time to renew those efforts is now, when they are needed most.

Taking a step back from the legal details, the evidence above suggests that solutions to the situation at the border may not lie exclusively in higher fences or stricter patrols but in smarter, more flexible entry policies that recognize the intricate dance between lawful and unlawful migration. In a world eager for solutions that respect the imperatives of national security, national prosperity, and human dignity, judicious use of lawful pathways need not be seen as a concession but as a cornerstone of effective border management.

Data Disclosure

This publication does not include a replication package.

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