Violent crimes are not “proportionally higher among black”. They are MUCH higher. Murders by blacks consist of almost HALF of all murders in America despite the fact that the young black men who commit the murders comprise only about 2% of the total population.
My wife is an OB, but on the way there almost became a psychiatrist and took all the required classes and most of the residency.
The dirty secret known in the mental health community (but you can barely find a paper on it, although they do exist) is that blacks have many multiple rates of “dark triad” mental illnesses, even when corrected for lower IQ — that is, 3-4 the rates of psychopaths/anti-social disorders, narcissism, inability to delay gratification, etc.
With whites in the middle, it’s blacks — whites/hispanics — Asians/Jews — on the rate of these mental disorders.
And while the data is not perfect, it appears to be be same outside the USA.
http://www.sciencedirect.com/science/article/pii/S0191886901000290