In the wake of the San Bernardino attack last December, U.S. Republican presidential candidate Donald Trump called for a ban on all Muslims entering the country. In an interview with Fox Business shortly after the attack, Trump explicitly connected the failed assimilation of Muslim immigrants to terrorism: “Go to Brussels. Go to Paris. Go to different places. There is something going on and it’s not good, where they want Shariah law, where they want this, where they want things that—you know, there has to be some assimilation. There is no assimilation.” Although most politicians, in both the U.S. Democratic and Republican parties and abroad, condemned Trump’s proposal for a ban on Muslim immigration, more than one-third of Americans and over half of Republicans support it.

Trump is tapping into a deep-rooted fear. It is the same fear that sustains the popularity of many extreme right-wing parties throughout Europe, from France’s National Front to Greece’s Golden Dawn. It is thus legitimate to ask whether the recent wave of immigration into Europe and the United States from Muslim-majority countries is compromising the safety of host populations. But the evidence suggests that the fears are misguided: Liberal democracies are not opening their doors to terrorism when they let in Muslim immigrants.

INTEGRATION AND DISCRIMINATION

Over the past year, unprecedented numbers of immigrants have left Muslim-majority countries to come to Europe, fleeing the carnage in Syria and the turmoil across North Africa. But these immigrants are not integrating well. In our book, Why Muslim Integration Fails in Christian-Heritage Societies (Harvard University Press 2016), we document the failure of Muslim immigrant integration in France and across Europe more broadly. Two immigrants who are alike in every single way except for their religious identity will integrate very differently within their host societies.

Migrants pray at a makeshift mosque in "The New Jungle" camp in Calais, France, August 2015. Peter Nicholls / Reuters

By studying a population of Senegalese Christian and Muslim immigrants from the Serer and Joola religiously mixed communities who migrated to France under identical conditions, we found that Muslim immigrants face greater discrimination in the labor market, earn less monthly income, express less attachment to their host country, and exhibit greater attachment to their country of origin than do their Christian counterparts. And these patterns do not improve in subsequent generations. The cause of this failure of integration is twofold: Islamophobia on the part of French society and Muslim immigrants’ tendency to identify more with their home communities in response. As a result, Europe is creating a class of under-employed immigrants who feel little or no connection with their host societies.

But linking Muslim immigration to terrorism is a mistake. Liberal societies should not condemn people simply for having the same cultural background as murderous criminals. (It would be as ludicrous as blaming all Italian-Americans for mafia killings.) Moreover, the obsession with Muslim immigration focuses on the wrong targets. Terrorists tend not to be poor, uneducated, or even, in many cases, of Muslim heritage. Olivier Roy, an expert on Islam, has used data from France’s “S File”—the French government’s antiterrorism watch list—to create an evidence-based portrait of today’s French jihadists. French jihadists are for the most part either second-generation French citizens—the children of relatively non-religious immigrants, who were born and raised in France—or native French converts—French citizens with no immigrant background who have converted to Islam. What unifies these two groups is not Islam; it is a sense of generational revolt. Similarly, among Western recruits who join the Islamic State (also known as ISIS), a disproportionate number are converts to Islam. This is why Roy describes the threat not as the radicalization of Islam but as the Islamization of radicalism.

Liberal democracies are not opening their doors to terrorism when they let in Muslim immigrants.

Today's terrorists are therefore not likely to be unemployed and uneducated religious Muslim immigrants fresh off the boat from North Africa or the Middle East. Instead, they tend to come from educated, relatively well-off families, and they often have engineering degrees. Usually, they come from secular backgrounds and join groups—economists call them “clubs”—that provide a strong sense of common bond with fellow members. Throughout the Muslim world, these Salafist clubs give their members material and emotional rewards if they demonstrate absolute loyalty. The only way members can demonstrate loyalty, however, is if they make it impossible for them to return to their former secular lives. They can then be persuaded to make ultimate sacrifices for the group, including suicide murder.

But it remains unclear why a reasonably stable and well-educated young man would join such a group. Our research in France points to one plausible explanation. We sent similar resumés of three applicants to French firms. All three were French citizens with secondary school degrees and several years of experience in middle-class jobs. By their names, employers could tell that one was Christian Senegalese, one was Muslim Senegalese, and the third was a native French person. One Senegalese applicant, randomly assigned to the Muslim or Christian name, was matched with the native French applicant for each job.

The results were clear. Employers were two and a half times more likely to offer the Christian an interview than the Muslim. In experimental games conducted in Paris’ nineteenth district where Serers and Joolas interacted with native French subjects, we once again found that the French exhibit a gratuitous distaste for Muslims, more so than they do for Senegalese Christians. When given the opportunity to withhold money from other people in the experiment, native French subjects were more likely to do so with Senegalese Muslims than with Senegalese Christians.

Employers were two and a half times more likely to offer the Christian an interview than the Muslim.

The implications of this distaste are significant. In a survey of 511 Muslim and Christian Serers and Joola living in France, we found that on average, Muslim Serer and Joola families earned 400 euros (roughly $455), or about 15 percent of an average French income, less per month than their Christian counterparts.

In other words, there was clear anti-Muslim discrimination in the competition for a middle-class job, which had significant implications for Muslims’ prospects of attaining a middle-class lifestyle. There is egregious discrimination in the French labor market. This discrimination led our Muslim respondents to view French institutions with much greater distrust than their Christian counterparts. Moreover, our Muslim respondents were more likely to send remittances back to Senegal and to plan to be buried there. Poverty does not draw these Muslims into Salafist clubs; reasonable yet unreachable ambitions do.

A Moroccan Muslim takes a photograph of himself in Mantes-la-Jolie, a suburb of Paris, July 2013. Youssef Boudlal / Reuters

Of course, discrimination in the labor market doesn’t turn graduates into killers. The actual number of members in Salafist clubs is so small (as a percentage of the overall population of potential recruits) that it defies any attempt to predict what makes someone susceptible. But education correlates with political activism, and where education does not fulfil life goals, religious clubs provide a compelling alternative.

Small nudges, such as publicizing discrimination rates, can raise awareness and reduce discrimination. Meanwhile, Muslim communities can do more to encourage gender equality and other norms of their host societies, for example, by shaming community members who refuse to take orders from women.

The one thing countries shouldn’t do is ban immigration.

On a macro level, firms should scrutinize their own hiring practices. They should also consider hiring consultants who can help them address tensions that arise due to workplace conflicts related to religion.

The one thing countries shouldn’t do is ban immigration. Such policies are directed at the wrong targets; they are also counter-productive. They do not tackle the discrimination Muslims face when trying to integrate into their host societies, and they may even exacerbate the failure of Muslim integration by encouraging Muslims to withdraw. The economists Eric Gould and Esteban Klor, for example, have shown that ten years after the September 11 attacks on the United States, Muslims living in states that saw a greater upsurge of Islamophobic acts are now less integrated into U.S. norms and culture: They tend to have higher fertility rates, lower rates of female participation in the labor market, and a weaker mastery of the English language. Trump’s proposals will no doubt further alienate the very community that the U.S. government must rely on to identify and stop known or would-be terrorists. After the Paris attacks of November 13, 2015, in which 130 people died, French authorities closed the country’s borders and launched a manhunt for the plot’s mastermind, Abdelhamid Abaaoud. They found and killed him a few days later. The informant who tipped off French authorities about his location? A fellow Muslim.