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We are thus witnessing a different pattern from early 20th century America, when growth in immigration from Europe, along with ethnic diversity more generally, was linked with increasing crime and formed a building block for what became known as “social disorganization” theory. New York today is a leading magnet for immigration, yet it has for a decade ranked as one of America’s safest cities. Crime in Los Angeles dropped considerably in the late 1990s (45 percent overall) as did other Hispanic influenced cities such as San Jose, Dallas, and Phoenix. The same can be said for cities smack on the border like El Paso and San Diego, which have long ranked as low-crime areas. Cities of concentrated immigration are some of the safest places around.

counterpoint

There are criticisms of these arguments, of course. To begin, the previous figure juxtaposes two trends and nothing more—correlation doesn’t equal causation. But it does demonstrate the trends are opposite of what’s commonly assumed, which is surely not irrelevant to the many, and strongly causal, claims that immigration increases crime. Descriptive facts are at the heart of sound social science, a first step in any causal inquiry.

Perhaps a bigger concern is that we need to distinguish illegal from legal immigration and focus on the many illegal aliens who allegedly are accounting for crime waves across the country—the “Newark phenomenon.” By one argument, because of deportation risk illegal immigrants are afraid to report crimes against them to the police, resulting in artificially low official estimates in the Hispanic community. But no evidence exists that reporting biases seriously affect estimates of the homicide victimization rate—unlike other crimes there is a body. At the national level, then, the homicides committed by illegal aliens in the United States are reflected in the data just like for everyone else. The bottom line is that as immigrants poured into the country, homicides plummeted. One could claim crime would decrease faster absent immigration inflows, but that’s a different argument and concedes my basic point.

There is also little disputing that in areas and times of high legal immigration we find accompanying surges of illegal entrants. It would be odd indeed if illegal aliens descended on areas with no other immigrants or where they had no pre-existing networks. And so it is that areas of concentrated immigration are magnets for illegal concentration. Because crime tends to be negatively associated with undifferentiated immigration measures, it follows that we can disconfirm the idea that increasing illegal immigration is associated with increasing crime.

Furthermore, our Chicago study did include both legal and illegal immigrants. I would estimate the illegal status at roughly a quarter—but in any case no group was excluded from the analysis. The other important point is that the violence estimates were based on confidential self-reports and not police statistics or other official sources of crime. Therefore, police arrest biases or undercounts can’t explain the fact that first generation immigrants self-report lower violence than the second generation, which in turn reports less than the third generation.

So let us proceed on the assumption of a substantial negative association across individuals, places, and time with respect to immigration and violence. What potential mechanisms might explain the connections and are they causal? Thinking about these questions requires attention be paid to confounding factors and competing explanations.

Social scientists worry a lot about selection bias because individuals differ in preferences and can, within means, select their environments. It has been widely hypothesized that immigrants, and Mexicans in particular, selectively migrate to the United States on characteristics that predispose them to low crime, such as motivation to work, ambition, and a desire not to be deported. Immigrants may also come from cultures where violence isn’t rewarded as a strategy for establishing reputation (to which I return below).

This scenario is undoubtedly the case and central to the argument—social selection is a causal mechanism. Namely, to the extent that more people predisposed to lower crime immigrate to the United States (we now have some 35 million people of foreign-born status), they will sharply increase the denominator of the crime rate while rarely appearing in the numerator. And in the neighborhoods of U.S. cities with high concentrations of immigrants, one would expect on selection grounds alone to find lower crime rates. Selection thus favors the argument that immigration may be causally linked to lower crime.

Another concern of social scientists is common sources of causation, or “competing” explanations. One candidate is economic trends. After all, potential immigrants respond to incentives and presumably choose to relocate when times are better in their destinations. Although a legitimate concern, economics can’t easily explain the story. Depending on the measure, economic trends aren’t isomorphic with either immigration or crime at either the beginning or end of the time series. Real wages were declining and inequality increasing in the 1990s by most accounts, which should have produced increases in crime by the logic of relative deprivation theory, which says that income gaps, not absolute poverty, are what matters. Broad economic indicators like stock market values did skyrocket but collapsed sharply while immigration didn’t.

Scholars in criminology have long searched for a sturdy link between national economic trends and violence, to little avail. The patterns just don’t match up well, and often they’re in the opposite direction of deprivation-based expectations. The best example is the 1960s when the economy markedly improved yet crime shot up. Don’t forget, too, the concentrated immigration and crime link remains when controlling for economic indicators.

Finally, the “Latino Paradox” in itself should put to rest the idea that economics is the go-to answer: Immigrant Latinos are poor and disadvantaged but at low risk for crime. Poor immigrant neighborhoods and immigrant-tinged cities like El Paso have similarly lower crime than their economic profile would suggest.

Competing explanations also can’t explain the Chicago findings. Immigrant youths committed less violence than natives after adjustment for a rich set of individual, family, and neighborhood confounders. Moreover, there’s an influence of immigrant concentration beyond the effects of individual immigrant status and other individual factors, and beyond neighborhood socioeconomic status and legal cynicism—previously shown to significantly predict violence. We estimated male violence by age for three types of neighborhoods (below):

• “Low-risk,” where a very high percentage of people work in professional and managerial occupations (90th percentile), few people hold cynical attitudes about the law and morality (10th percentile), and there are no immigrants;
• “High-risk,” where professional/managerial jobs are scarce, cynicism is pervasive, and there are also no immigrants;
• “High-risk, immigrant neighborhoods,’ defined by similarly low shares of professional/managerial workers and high legal cynicism, but where about one-half of the people are immigrants.

The estimated probability an average male living in a high-risk neighborhood without immigrants will engage in violence is almost 25 percent higher than in the high-risk, immigrant neighborhood, a pattern again suggesting the protective, rather than crime-generating, influence of immigrant concentration.

Finally, we examined violence in Chicago neighborhoods by a foreign-born diversity index capturing 100 countries of birth from around the world (page 32). In both high- and low-poverty communities, foreign-born diversity is clearly and strongly linked to lower violence. Concentrated poverty predicts more violence (note the high poverty areas above the prediction line) but violence is lower as diversity goes up for low- and high-poverty neighborhoods alike. Interestingly, the link between lower violence and diversity is strongest in the most disadvantaged neighborhoods.