Enforcement and illegal migration Updated

Modeling immigration enforcement

Increasing border enforcement has been the preferred response for confronting rising numbers of unauthorized immigrants. Voters and their governments view illegal immigration as undesirable for a number of reasons. Unauthorized immigrants are typically low-skilled and relatively poor. They bring little in the way of savings to invest or formal training to put to use in the destination country labor market. In many countries, although typically not in the US, they tend to work off the books. Increasingly in recent years, they are applying for asylum. Some groups say unauthorized immigrants are more likely to commit crime but the evidence does not support that claim. Illegal immigration is also often viewed as symptomatic of the government's lack of control over the nation's borders. This is regarded as a politically unacceptable weakness in some quarters, especially in the context of concern about national defense and the need for protections against terrorism.

Governments may also intervene to protect the employment prospects of native workers. Research shows that low-skilled foreign workers have a small negative effect on competing natives’ wages. Research also shows that low-education immigrants cost more in public services than they contribute in taxes, making them a net fiscal burden on taxpayers.

In theoretical models of illegal immigration and the application of border and interior enforcement, unauthorized immigrants are usually assumed to be low-skilled and relatively poor [1]. Increased border enforcement raises the unskilled wage, which helps unskilled workers, but it also raises taxes to fund enforcement, which hurts native skilled workers. By raising the unskilled wage and thus increasing the gains from migration, border enforcement is counterproductive. Interior enforcement does the opposite, pushing down the wages of unauthorized workers (assuming that employers can distinguish between legal and unauthorized workers, which is not always the case).

By increasing the costs of migration, enforcement affects both the volume and the composition of migrant flows. Research shows that when the costs of migration are high, possibly due in part to increased enforcement, low-education, low-income workers simply may not be able to afford to migrate. For example, Mexican migrants with low levels of education are deterred more by increased border enforcement than their better-educated peers, resulting in positive selection among unauthorized migrants [2].

The migration decision

Migration can be forced, voluntary, or a combination of the two. Civil war, persecution, or famine may leave people with little choice but to migrate. With voluntary migration, theory posits that a potential migrant decides to migrate if the expected benefits—typically earnings from a job—exceed the costs, such as traveling expenses, smugglers’ fees, and the costs of adapting to the destination country [2]. This basic model falls short of explaining several well-established patterns, such as circular or return migration. Return migrants may be motivated by target saving—the desire to accumulate a predetermined sum to pay off a debt or invest in a business. Moreover, the migration decision is often made at the household rather than the individual level [3]. People may migrate to reunite with earlier migrants (network migration). People living in countries with incomplete financial markets and weak social safety nets may migrate not only to increase income but also to diversify risk to household income from economic crises, crop failures, and similar shocks. It bears noting that climate change may be contributing to the frequency and severity of some of these shocks.

Whatever the details of the migration model, migration costs figure prominently for two reasons. First, pecuniary costs have to be paid up front, which requires access to savings or credit (borrowing). Second, illegal migration is more costly than legal migration because unauthorized migrants typically pay a smuggler in addition to risking their lives. Their trips are also generally longer, which entails more foregone labor income, particularly if migrants are apprehended and detained before they are deported, as is increasingly the case along the US–Mexico border [4].

Migration models highlight the importance of the income gap, which is driven by wages and job opportunities in both destination and origin countries. There is typically a higher responsiveness of illegal than legal migration to changing economic conditions [5], [6]. This was apparent in southern Europe during the economic boom in the early 2000s (preceding the sovereign debt crisis). Unauthorized migration to the US has a long history of disproportionately large response to changes in labor demand, particularly in construction [6]. Border Patrol apprehensions are highly correlated with construction permits for single-family housing, and illegal immigration plummeted during the 2007–2009 recession and housing bust [6], [7].

In addition to business cycle factors, which tend to be temporary, there are long-term supply-side factors such as demographics. Large birth cohorts in origin countries depress relative wages as young people enter the workforce, which widens the income gap and contributes to emigration. Similarly, declining fertility rates depress population growth, speed up aging, and reduce emigration. In Mexico, fertility rates fell from 6.8 children per woman in the late 1970s to 2.2 children per woman in 2010, contributing to falling emigration and making resumption of mass emigration from Mexico unlikely [6], [7].

Trends in border enforcement

Tougher immigration enforcement has been the trend around the world since the 1990s. Australia implemented mandatory detention in 1992, which puts all unauthorized immigrants into detention camps while their cases are resolved, a process that can take years. In the mid-2000s, the EU implemented its own border enforcement, adding border guards and sea patrols and creating Frontex, the European Agency for the Management of Operational Cooperation at the External Borders of the Member States of the European Union. US border enforcement rose sharply in the 1990s and 2000s, but the buildup slowed after 2010. The number of US Border Patrol agents rose from 4,139 in 1992 to 21,444 in 2011 before shrinking to 19,555 in 2018. Over this time, the Border Patrol also invested in advanced technology, including double fences, watch towers, ground sensors, remote video monitoring, and aerial and marine surveillance. By 2012, about one-third of the southwest border of the US was fenced and it remained at that level until recently when the Trump administration began building new barriers [6], [8].

There has also been a trend toward harsher punishments for migrants apprehended at US borders. Historically, the great majority of apprehended migrants were from Mexico; they signed “voluntary departure contracts,” after which they boarded a bus back to Mexico. Some observers referred to this policy as the “revolving door” of US border enforcement because the departed migrants typically attempted another border crossing within a day or two. This process repeated itself until the migrant was successful [8]. Two important changes spelled the beginning of the end of this practice. One, the Border Patrol began fingerprinting all apprehended migrants, which allowed them to identify and prosecute repeat crossers. Two, Congress began mandating harsher consequences for apprehended migrants. The Illegal Immigration Reform and Immigrant Responsibility Act, passed in 1996, implemented expedited removal, interior repatriation, and three- and ten-year admission bars for previously admitted unauthorized immigrants seeking to be admitted legally to the US. Several other initiatives followed, including “zero-tolerance” policies such as Operation Streamline, which subjects unauthorized immigrants to federal criminal prosecution [8]. So-called “zero-tolerance” and “consequence” policies implemented by the US Border Patrol increased the share of apprehended migrants subject to administrative and criminal sanctions from 15% in 2008 to 85% in 2012. While most offenses were misdemeanors and resulted in very short jail terms, the proliferation of zero-tolerance practices along the US–Mexico border marks a dramatic shift from the days of voluntary departure.

During the massive border buildup and implementation of tougher consequences, migrant apprehensions first rose sharply, peaking at 1.7 million (rounding) apprehensions in fiscal 2000, and then plummeted, averaging just below 400,000 from 2011 to 2018. Meanwhile, the estimated unauthorized immigrant population rose from 3.5 million to 12.2 million between 1990 and 2007 before declining to 10.5 million in 2017 (Figure 1) [7]. The US is home to an estimated one-quarter of the world's unauthorized immigrants. Not all of them cross the border illegally, however. In fact, in recent years more unauthorized immigrants have overstayed visas than entered the country illegally [8].

Is border enforcement an effective deterrent?

Border enforcement, by increasing the probability of apprehension or the severity of punishment, should deter illegal immigration. Despite this clear prediction, the US experience since the 1990s suggests that massive increases in border enforcement are consistent with both rising and falling inflows of unauthorized immigrants. Clearly, border enforcement is just one of many migration determinants.

The first attempts at border buildups were likely more effective in diverting migrants than deterring them [3]. Earlier studies on Mexico–US migration find little direct evidence of deterrence effects of border enforcement on migration but considerable evidence of migrants’ adaptive behavior. For example, large, localized ramp-ups in border enforcement in the US such as Operation Hold the Line in El Paso in 1993 and Operation Gatekeeper in San Diego in 1994 led to steep declines in migrant apprehensions in these sectors but increases in Tucson (Figure 2) [3]. Instead of crossing through urban areas in West Texas and Southern California, migrants went through the deserts of Arizona [3]. Later, when the Border Patrol cracked down on the Arizona border, migrants shifted to South Texas. By forcing migrant crossings to desolate or dangerous areas, US Border Patrol increased the risk of migrant injury and death. Enforcement also encouraged other adaptive behavior, such as inventive crossing techniques, including the use of decoys and tunnels.

Increased US border enforcement has had several other effects that also deter migration. The probability of using a smuggler increased from 80% in 1990 to 90% in 2012, perhaps because fewer migrants were willing to cross alone through the wilderness [8]. Smuggler fees also rose along with demand, and successful crossings grew more difficult and took longer [4]. Migrant surveys, such as the Mexican Migration Project, indicate that smuggler prices for Mexicans rose in inflation-adjusted terms from less than US$1,000 a trip in the 1980s to over US$5,000 in 2013. Only some of the increase can be attributed to more border enforcement, however, and the rest to other demand and supply factors. One study found that the border buildup between 1986 and 2004 raised smugglers’ prices by only 17% while increasing crossing time by two to five days [4]. Higher smuggler and opportunity costs should translate into a lower probability of migrating. Indeed, another study found that a 20% rise in smugglers’ prices led to a 13–21% decline in the probability of migrating [8].

Among studies that measure the direct relationship between border enforcement and illegal immigration, one set of estimates suggests that a 10% increase in Border Patrol linewatch hours reduces illegal inflows by 4–8% and that this effect increases over time [9]. Another study finds that a 0.5 million increase in linewatch hours—the average increase between 1990 and 2003—reduced intentions to re-migrate among a sample of male return migrants by roughly 14% [10]. Tougher border enforcement is also correlated with lower wages in Mexican border cities, suggesting that enforcement prevents or delays illegal entries into the US [5]. Taken together, these findings show that border enforcement is an effective “at the border” deterrent—increasing Border Patrol watch hours reduces the probability that migrants intend to repeat border crossings or delays their attempts [6]. Studies that find that border enforcement raises smuggling prices and thus depresses migration at the origin document a form of “behind the border” deterrence, which prevents the potential immigrant from attempting a crossing [6].

Trends in interior enforcement

Interior enforcement has been ramped up in many countries, but perhaps nowhere as drastically as in the US, which deported a record three million immigrants from 2010 to 2017. Record deportations are partly the result of new programs that have incorporated state and local police into federal immigration enforcement efforts. The impetus for this change was the 287(g) provision in the 1996 Illegal Immigration Reform and Immigrant Responsibility Act (IIRIRA) under which state and local police departments could opt to be trained and deputized to enforce federal immigration laws. Another program, Secure Communities, came later—in 2008—but was in place nationwide by 2013. Secure Communities checks the records of arrested individuals against immigration databases [6]. Research has linked Secure Communities and the 287(g) program to hundreds of thousands of deportations but also to adverse outcomes for immigrant families, including worse labor market and health outcomes, increased home foreclosures, separation of children from their parents, higher probability of children dropping out of school and of grade retention (repeating an academic year of school), among others.

Employers have also been targeted. While the Immigration Reform and Control Act of 1986 made it illegal to hire unauthorized immigrants, the law was rarely enforced. This changed with E-Verify, which allows employers to check the legal working status of new hires against Social Security records and a federal immigration database. E-Verify is now mandatory for federal government contractors and is used to varying degrees in over 20 states. Although most states do not require that employers use E-Verify, estimates suggest over half of all new hires in the US go through it.

Several studies have found that state-level universal E-Verify requirements reduce the population of unauthorized immigrants and worsen their labor market outcomes. For instance, implementation of the 2007 Legal Arizona Workers Act, which requires all employers to use the E-Verify program, resulted in a large shift out of wage and salary employment and into self-employment among non-citizen Hispanic immigrants, a group with a high share of unauthorized workers [11]. Another empirical analysis finds that E-Verify mandates more broadly severely reduce hourly earnings of immigrants who are most likely to be unauthorized, suggesting that such programs may be successful in reducing the rewards of illegal immigration [12]. Meanwhile, there is some evidence that E-Verify raises wages for competing groups of US workers, including Hispanic natives and naturalized immigrants.

Unintended consequences