An amazing chart from economist Amir Sufi, based on the work of Emmanuel Saez and Gabriel Zucman, shows that when you look inside the 1 percent, you see clearly that most of them aren’t growing their share of wealth at all. In fact, the gain in wealth share is all about the top 0.1 percent of the country. While nine-tenths of the top percentile hasn’t seen much change at all since 1960, the 0.01 percent has essentially quadrupled its share of the country’s wealth in half a century.

It turns out that wealth inequality isn’t about the 1 percent v. the 99 percent at all. It’s about the 0.1 percent v. the 99.9 percent (or, really, the 0.01 percent vs. the 99.99 percent, if you like). Long-story-short is that this group, comprised mostly of bankers and CEOs, is riding the stock market to pick up extraordinary investment income. And it’s this investment income, rather than ordinary earned income, that’s creating this extraordinary wealth gap.

The 0.1 percent isn’t the same group of people every year. There’s considerable churn at the tippy-top. For example, consider the “Fortunate 400,” the IRS’s annual list of the 400 richest tax returns in the country. Between 1992 and 2008, 3,672 different taxpayers appeared on the Fortunate 400 list. Just one percent of the Fortunate 400—four households—appeared on the list all 17 years.