Sunday, March 5, 2017

Immigration and Crime – What the Research Says

The alleged murder of Kate Steinle in San Francisco by illegal immigrant Juan Francisco Lopez-Sanchez has reignited the debate over the link between immigration and crime. Such debates often call for change in policy regarding the deportation or apprehension of illegal immigrants. However, if policies should change, it should not be in reaction to a single tragic murder.  It should be in response to careful research on whether immigrants actually boost the U.S. crime rates.

With few exceptions, immigrants are less crime prone than natives or have no effect on crime rates.  As described below, the research is fairly one-sided.      

There are two broad types of studies that investigate immigrant criminality.  The first type uses Census and American Community Survey (ACS) data from the institutionalized population and broadly concludes that immigrants are less crime prone than the native-born population.  It is important to note that immigrants convicted of crimes serve their sentences before being deported with few exceptions.  However, there are some potential problems with Census-based studies that could lead to inaccurate results.  That’s where the second type of study comes in.  The second type is a macro level analysis to judge the impact of immigration on crime rates, generally finding that increased immigration does not increase crime and sometimes even causes crime rates to fall.

Type 1: Immigrant Crime – Censuses of the Institutionalized Population

Butcher and Piehl examine the incarceration rates for men aged 18-40 in the 1980, 1990, and 2000 Censuses.  In each year immigrants are less likely to be incarcerated than natives with the gap widening each decade.  By 2000, immigrants have incarceration rates that are one-fifth those of the native-born.  Butcher and Piehl wrote another paper focusing on immigrant incarceration in California by looking at both property and violent crimes by city.  Between years 2000 and 2005, California cities with large inflows of recent immigrants tended have lower violent crimes rates and the findings are statistically significant.  During the same time period, there is no statistically significant relationship between immigration and property crime.

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