From Opinion Journal on Tuesday:
A Treasury study refutes populist hokum about "income inequality."
OK, "hokum" is our word. The study, to be released today, is a careful, detailed piece of research by professional economists that avoids political judgments. But what it does do is show beyond doubt that the U.S. remains a dynamic society marked by rapid and mostly upward income mobility. Much as they always have, Americans on the bottom rungs of the economic ladder continue to climb into the middle and sometimes upper classes in remarkably short periods of time.
Whole thing here. Chart is from the article.