When groups of impoverished people see chances to move up in society, but are marginalized by society, crime is created.
Because the Italians were not accepted into society, some within their communities began to dominate those communities.
In these neighborhoods, if business owners did not pay the Mafia, then their businesses would be destroyed. In such a tight knit community, no one sought outside help.
The same thing happened in the 1960's and 70's with African Americans who were not accepted into society.
With the absence of law enforcement and impoverished living conditions, on the outskirts of affluent cities, crime amongst Black Communities began
Eventually, the Irish and Italians simulated into society. This having to do partly with their caucasian appearance.
African - Americans however, are much easier to identify than an Irish or Italian might be.
When the chances of escaping poverty are so small- some turn to crime to fulfill their needs.
The more densely populated the area, the higher the crime rate. Typically densely populated areas are impoverished and many have only a small space to call their own.
If Syrian refugees come to the United States and are marginalized, then Syrian criminal gangs will form