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Does Fortifying the Mexican Border Keep Unauthorized Immigrants from Coming to the United States?

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University of California-San Diego

In overheated arguments about immigration, politicians often proclaim that we must do everything possible to fortify the 2000-mile U.S. border with Mexico – the country from which more than three-fifths of undocumented migrants arrive. Both Republicans and Democrats in Congress push for fortification, and some hard-liners have even called for electrified fences.

But does a fortified border accomplish what its supporters intend? What do we know about efforts to build barriers so far – and what can we conclude about the likely future effects?

An Expensive Buildup

One thing is certain: it is not cheap to try to prevent people from moving back and forth across a long land frontier. Since the mid-1990s, the U.S. government has poured unprecedented resources into the effort.

  • From 1996 to 2011, the number of Border Patrol agents rose from 5,900 to more than 21,000.

  • At many parts of the Mexican border, new fencing and sophisticated surveillance systems have been installed.

  • The 2012 budget for the Department of Homeland Security soared to include $11.7 billion for Customs and Border Protection, plus another $5.9 billion for Immigration and Customs Enforcement. Much of the money was spent on the southern border.

Has this remarkable buildup succeeded in deterring unauthorized immigration from Mexico? We can start by asking about immediate deterrence – how many people who have tried to get into the United States without proper papers were turned back? Later, we will look at the more fundamental issue of remote deterrence – factors that keep would-be migrants from deciding to leave homes south of the border in the first place.

Does Fortification Keep Undocumented Immigrants Out?

At the beginning of the border buildup, undocumented people trying to enter the United States were apprehended about one million times each year – usually along the southwest border. The number of apprehensions increased to 1.6 million in 2000, before declining to 340,000 in 2011. We need to keep in mind, though, that these numbers refer to events in which an undocumented would-be entrant was captured. The same person could have tried to enter the country several times and might have been caught more than once.

A different kind of evidence comes from government surveys and census records of the people who live in the United States. Based on this evidence, the estimated population of unauthorized immigrants from Mexico grew from 4.7 million in 2000 to 7 million in 2008, and then declined slightly to 6.1 million in 2011. In other words, for at least the first decade and a half of efforts to fortify the border, the federal government’s own data reveal a dramatic increase in the number of unauthorized Mexicans living in the United States.

The most obvious effect of fortifications was to keep unauthorized immigrants in the United States after they crossed the border. Undocumented arrivals became increasingly likely to just stay in the United States for long periods – to avoid the physical risks and high costs of repeatedly going back and forth in clandestine crossings.

The Department of Homeland Security credits enforcement with reducing the undocumented population, but we should be skeptical. The most notable declines occurred after the U.S. economy went into recession in 2008. Job losses in sectors such as construction – where undocumented Mexican immigrants are often employed – probably had at least as large an impact as tighter border enforcement.

Overall, there is little evidence that people determined to get into the United States are permanently kept out, no matter how many are turned back at any given time. Between 2005 and 2011, the Center for Comparative Immigration Studies at the University of California, San Diego, interviewed unauthorized migrants in three small Mexican towns and the U.S. destinations to which people from those towns migrated. Depending on the community, between 24 and 47 percent were apprehended on their most recent attempt to cross the U.S. border. But between 92 and 98 percent eventually crossed the border successfully. Usually people made it on the second attempt if apprehended the first time. Since the 1980s, unauthorized migrants have consistently gotten across the border at a high rate – though the percent apprehended at least once varies. Most Mexicans determined to come to the United States get here sooner or later.

The Consequences of Making It Harder to Cross the Border

Tough border enforcement efforts have unleashed unintended consequences. More unauthorized migrants now use coyotes to smuggle them door-to-door for a set fee, which has increased from several hundred dollars in the early 1990s to around $3000 in the early 2010s.

And migrants are not just paying more; they are also more likely to die. Border enforcement concentrated in urban areas pushes migrants to try to cross in remote desert and mountainous regions where journeys take up to four days on foot. Between 1994 and 2009, more than 5000 migrant deaths were recorded, an average of one a day. Immigration officials acknowledge using dangerous geography as a deterrent.

The threat of dying in the desert can discourage potential migrants from planning to migrate at all. In 2011, respondents in Mexico were asked if they intended to try to get into the United States in the coming year. Those who believed it would be very dangerous to cross the border were less likely to say they planned to try – and so were people who thought the U.S. economy was in bad shape. But if the U.S. economy begins creating large numbers of jobs again, more workers south of the border will gain new determination to cross the frontier. And most who try will eventually succeed. Fortifications alone cannot permanently deter undocumented immigration.