A brief excerpt:
In 1975, ...the top 0.1 percent of earners garnered about 2.5 percent of the nation’s income, including capital gains, according to data collected by University of California economist Emmanuel Saez. By 2008, that share had quadrupled and stood at 10.4 percent.
The phenomenon is even more pronounced at even higher levels of income. The share of the income commanded by the top 0.01 percent rose from 0.85 percent to 5.03 percent over that period. For the 15,000 families in that group, average income now stands at $27 million [per family per year, presumably].