You probably saw a TED video of Hans Rosling introducing it a few years back. Now you can make your own comparisons. Admittedly all data doesn't exist for every year (2005 is the only year with income distribution data for China, for example).

But the 2nd poorest quintile in China made 9.8% of the total, and the second richest 22% of the total (2005). Corresponding numbers for the US is 11% and 22.4% (2000). The American income per capita is about 10x bigger though, adjusted for inflation and purchasing power. But remember that the richest 20% in China represents as many people as the US population.