Evidence that the Rich are Getting Richer

The top 10% are getting rich at a much faster rate than the remaining 90% of the population. Why? I think those who own capital are busy, not in working 9-5s but in applying their capital to maximize RoI. So if the economy is growing at X%, the top 10% grow at 10X the rate!

Ref: http://en.wikipedia.org/wiki/Economy_of_USA