The El Salvador national flag hangs outside the Consulate General of El Salvador in New York City. (Reuters)

At the Jan. 30 State of the Union, President Trump made a point of talking about the danger of Mara Salvatrucha (MS-13), a primarily Salvadoran gang.

Last month, the Trump administration announced plans to revoke temporary protected status for Salvadorans, which allows nearly 200,000 Salvadorans to live and work in the United States. The decision stems not only from the president’s immigration agenda but also from deep anxieties in the United States about MS-13.

The irony is that MS-13, like its 18th Street gang rivals, is itself the consequence of a previous massive U.S. deportation wave that returned Salvadoran gang members from Los Angeles, starting in the 1990s. This cycle could repeat itself, even for returnees without any criminal record, if they overwhelm El Salvador’s capacity to receive them.

My research, which looks at detailed data on deportations and crime and is featured in Crisis Group’s recent report, “El Salvador’s Politics of Perpetual Violence,” examines the unanticipated consequences of about four decades of U.S. immigration policy.

Deportations to El Salvador meant more gang recruitment

During the Carter and Reagan administrations, as U.S. aid fueled the Salvadoran civil war, about 2 million Salvadorans fleeing the conflict initially found refuge in the United States, particularly Los Angeles. Caught on the tough streets of Los Angeles, some poor, young Salvadorans joined existing gangs while others established their own, the MS-13. The U.S. government later returned many of them to El Salvador — but these Salvadorans were now armed with drug-selling, extortion, kidnapping and other criminal skills.

As part of Crisis Group’s Economics of Conflict initiative, I examined what happened when Salvadorans returned home in the 1990s and 2000s to shed light on what we might expect today. Analysis of official U.S. and El Salvador data on deportations and crime reveals U.S. migration policy produced some unintended consequences, particularly for education and gang recruitment.

And there was another consequence: Over the long term, deportations to El Salvador fueled child migration back to the United States, as young Salvadorans sought to escape the growing violence.

U.S. deportations stepped up significantly in the 1990s and 2000s, with the passage of the 1996 Illegal Immigration Reform and Immigrant Responsibility Act and the 2002 Homeland Security Act. Without opportunities at home, some of the thousands of deported Salvadorans turned to the criminal skills they had learned in the United States. The data show a clear link between deportations of criminals/gang members and a rise in homicide rates in El Salvador (see graph).

Homicide rates in municipalities with low and high gang presence, and yearly criminal deportations. Data: El Salvador National Civilian Police and U.S. Department of Homeland Security.

The data tells us that violence in El Salvador increased at the same time and in the same places where gangs with U.S. origin settled. Gangs especially targeted children in El Salvador, forcing them at a young age to choose between victimization or gang membership.

Children born in the areas where gang members settled were more likely to commit crimes themselves; as adults, such individuals were about 30 percent more likely to be involved in gang-related crimes than adults who grew up in locations without gangs, or who were already adults at the time the gang deportees arrived. In addition, I find that human capital investments were also affected: Individuals exposed to gangs during childhood had many fewer years of education than those with less exposure.

Deteriorating conditions turned El Salvador into one of the world’s most violent countries supposedly at peace, a major factor precipitating the flight of 100,000 Salvadorans in recent years. Of the unaccompanied minors among them, some 66 percent cited violence as their main reason for leaving.

These young Salvadorans hailed disproportionately from the areas where the first wave of criminal deportees settled. Using as proxy for child migration the number of Salvadoran returned children per month, the map below shows the large number of young emigrants leaving El Salvador from municipalities with higher rates of homicides, generally caused by gang violence. I find than on average, for every 10 homicides per month in a municipality, three additional children from that area left the country.

Map of origins of Salvadoran deported children and average local homicide rates 2003-2016. Data: International Organization for Migration (IOM; El Salvador National Civil Police.)

This research highlights the core issue facing U.S. policymakers: Ending temporary protected status is likely to have unintended harmful consequences in the long run. True, these law-abiding Salvadorans under threat of deportation today are distinct from criminal deportees of the 1990s or of recent years (over 1,200 gang members were deported from the United States to El Salvador last year).

The vast majority are simply trying to make a better life for themselves and their family in America. However, El Salvador’s poor security and anemic economic growth likely will expose them to great strain, including the risk of gang victimization and recruitment.

Assuming the United States proceeds with this new round of deportations after the TPS expires in 2019, what is El Salvador’s best bet for the migrants’ safe return? The country’s history suggests that reducing the poverty and alienation that put the last generation of returnees at risk of gang recruitment would help reduce migration-related violence.

Specifically, this would mean expanding work and educational opportunities in areas that receive more returnees. There are ways to jump-start this process by harnessing the skills of returnees. The New Yorker, for instance, recently highlighted how call centers employ returning Salvadorans with a strong command of English. Other avenues include taking advantage of the entrepreneurial skills returnees acquired in the U.S. service industry or providing certification at home for skills acquired in the United States.

Social integration tends to reduce violence in general, but even more so in El Salvador, where strong social and community bonds could stop gang recruitment and expansion. My examination of historical maps shows that the areas best able to keep gangs at bay are those where the armed insurgency was strongest during El Salvador’s civil war (1980-1992). Those places, with robust communal ties and a history of wartime collective mobilization, suffer relatively fewer homicides and gang recruitment of children.

The United States and El Salvador share this entwined history of terrifying gang violence. Deporting yet more Salvadorans to a homeland with limited professional opportunities seems an open invitation to continued cycles of violence.

Micaela Sviatschi, a nonresident Economics of Conflict Fellow at International Crisis Group, teaches economics and public affairs at Princeton University. Her research focuses on development economics with a focus on human capital, labor and crime.