The numbers are at purchasing power parity--critical for cross-country comparisons. And the chart "shows the relationship between a) the distribution of income by "ventiles" (5% groups) for the U.S., Brazil, China and India on the horizontal axis and b) the percentile of world income distribution on the vertical axis." That means, for America, according to Catherine:
Notice how the entire line for the United States resides in the top portion of the graph? That’s because the entire country is relatively rich. In fact, America’s bottom ventile is still richer than most of the world: That is, the typical person in the bottom 5 percent of the American income distribution is still richer than 68 percent of the world’s inhabitants.In other words, America's poor are comparatively well-off. More evidence that income inequality mostly is meaningless (in part because it reflects return to talent).
Now check out the line for India. India’s poorest ventile corresponds with the 4th poorest percentile worldwide. And its richest? The 68th percentile. Yes, that’s right: America’s poorest are, as a group, about as rich as India’s richest.