There are 2 primary reasons for this.
Whites tend to be involved more in the stock market which has been doing remarkably well during a period of otherwise dismal economic recovery. For instance, my partner who works in the industry has very few non-white clients interested in investing money -- not because he only wants to work with white clients but because they are overwhelmingly the ones interested. This has allowed many whites who took big losses during the crash to make up for their losses again, whereas many blacks and latinos and even asians who were very successful before the crash had a lot of their worth in property and other ventures that were most affected by the crash, and have not compensated in other ways.
The other reason is that whites are having fewer and fewer children and are concentrating their wealth. All I have to do is think of all the uncles and aunts who don't have any children and end up putting their nieces and nephews in their will along with the parents/grandparents who are already passing on their money to maybe 1 or 2 grandchildren in the family who end up with head start and a car, a house, etc.
The Latino population on the other hand is growing by leaps and bounds but without the financial support for it. This keeps them in a cycle of poverty, just like the huge populations of white families were during the depression.
Blacks on the other hand, although they have above average birthrates also have a high mortality rate that keeps their numbers down although they are expected to still grow in coming years. Unfortunately some blacks have been caught in a cycle of poverty because of several reasons that I won't elaborate on now.
The Asian community, while traditionally the wealthiest race per capita has been exploding population wise and there has been a major immigration influx of very poor "Asians" like Hmongs (in Wisconsin and Minnesota their numbers are skyrocketing) who are very similar to the Latino community in terms of large-scale familial growth -- unlike the Japanese Americans or Chinese Americans who have a smaller number.