According to the old adage, "the rich get richer and the poor get poorer." But the real story is far more complicated.
Take a look, for example, at Gapminder.org, a site that looks at global economic and human development trends—and that does a fantastic job of helping people visualize complicated data. Their most recent take on global income distribution offers competing insights: material wealth has increased since 1970, but in the U.S. at least, so has income stratification.