While some left-of-center media outlets claim that no relationship exists between immigration and crime in specific areas of Europe (or that immigration even reduces crime), the story is certainly more complex when you look at broad areas of the region and focus on violent crime.

If we consider the countries of northwestern continental Europe shown in the map below (Austria, Belgium, Czech Republic, Denmark, France, Finland, Germany, Netherlands, Norway, and Sweden), and then consider changes in the international migrant stock (number of people born in a country other than that in which they live, including refugees -- available at five-year intervals starting in 1960), real per capita GDP, the unemployment rate, and the population normalized rate of violent crime, a possible story emerges.

It is clear that within this group of European nations, higher net rates of immigration (i.e., greater changes in the international migrant stock as a percentage of total population) correlate very strongly with more rapid increases in violent crime rates.

Accounting for different rates of change in the unemployment rate and real per capita GDP (on a purchasing power parity basis) among these countries only adds support to the hypothesis that higher rates of immigration may be destabilizing these societies. Neither changing unemployment rate nor changing real per capita GDP yields a significant correlation with changing violent crime rates over this time frame, whereas changing immigration rates have significant correlations with changing violent crime rates regardless of whether the other variables are included in a regression model or not.

These types of findings are consistent with what we are seeing and hearing from Europe. Media reports show that a rising tide of citizens throughout the continent -- and across the political spectrum -- are starting to express concerns over the high rates of immigration during the past two decades.

At modest rates, immigration can be a positive influence on a nation's socioeconomic structure, with newcomers bringing forth ideas and vitality. But when immigration rates are too high, particularly during otherwise difficult economic periods, social destabilization and economic resentment can set in. The political goal is to find the optimum rate of immigration. Some regions of Europe appear to be well above their optimum range, and may need decades of an effective halt to net immigration in order to let the unrest settle down.