Silicon Valley may have plenty of millionaires, but the road to U.S. billionairedom is increasingly paved through finance. Nearly 27% of all U.S. billionaires in 2014 worked in finance (read: hedge-fund managers and a few others), according to a study by Caroline Freund, a senior fellow at the Peterson Institute for International Economics, and Sarah Oliver, a research analyst at the Washington, D.C.-based think tank. By comparison, just under 12% did in 1996, they said. The U.S. stands out from other advanced economies, both in finance as a source of wealth and in the comparatively small portion of those whose billionaire status comes through inherited wealth (although there are still plenty of those).

http://www.marketwatch.com/story/finance-not-tech-is-driving-growth-in-us-billionaires-2016-02-25