Migrants are usually poor, and if there are not enough resources and opportunities available, it is easy to turn to crime. Migrants are not more violent than citizens by nature, but a lack of opportunities can increase the potential for young migrants to increase crime of an area. The migrants aren't necessarily the problem, but the attitudes of the citizens and opportunities in a country are.
Since the arrival of over 1million migrants from the Middle east, Africa and South Asia, to Europe, crime, especially rape has increased dramatically. There have been tens of thousands of crimes committed by recent migrants in Europe within the passed year. http://www.gatestoneinstitute.org/6527/migrants-rape-germany
Here's one example from Saxony Germany. From January to September 2015, the Saxon government recorded 4,695 immigrants as the prime suspects in crime committed, and 10,397 offences. This is compared to 3,104 immigrant criminals and 7,029 offences in the same period over 2014. There was 47 per cent increase in 2015.
Plus there have been many cases of migrants committing mass molestation in Cologne, Hamburg, Stuttgart, Sweden and Finland.
Migrants do not increase crime rate in Euporean countries or anywhere else for that matter. Poverty, and the lack of education and opportunities is what increases crime. Unfortunately, it just so happens that some migrants are in these kinds of situations, which leads them to turn to violence and crime as a way to earn a living.
Any time you send in millions of poor desperate citizens into a place, crime will increase. It's just the nature of the thing. Migrant workers are destroying the social fabric of Europe and must be removed at all costs. Why can't the poor people just stay where they are and leave us in peace?
Migrants do not increase crime in European countries. It is my belief that most migrants come to different countries for the sole purpose to find work to support themselves and their families. While there may be some percentage of criminals in the population of migrants in Europe, that number is most likely representative of the percentage of crime throughout Europe. Therefore it is a generalization to say that migrants will increase the crime rate in European nations.