What causes the stark differences between black American unemployment and that for the rest of the country, a gap that is not improving? The reasons are not simple, and there is no single dominant one. Among them is that black unemployment in large urban populations is often much higher than the national average for black Americans. This tends to push the national average up because of the large portion of Americans who live in big cities. For example, over 80% of the population of Detroit is black, and the unemployment rate there is still well above the national average.