Perhaps one of the reasons could be, that once employed they are much harder to sack, due to the fear of a potential employer, that later they may take up the race card, which in turn could cost many thousands of pounds in a law suite.
This is just common sense on the part of an employer, just as some tend to shy away from employing females of childbearing age, due to all the legislation that has recently been brought out for their protection.
I am not saying these numerous protection clauses should not be in force, but it may have something to do why certain factions are more likely than others to be unemployed.