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).

“Over 40% of the growth in the total U.S. billionaire population is attributable to growth in financial-sector billionaires, as compared with 14% in Europe and 12% in other advanced economies,” they wrote.

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Even so, finance isn’t the biggest source of U.S. billionaires, they found. That remains inherited wealth (29%, down from 52% in 1996) and company founders (32%, little changed from 1996).

A new source of U.S. billionaires are those with connections to politics or to resources (primarily natural-resource extraction and energy), at nearly 4% in 2014 compared to none in 1996.

Finance isn’t quite the same source of extreme wealth in other developed countries. The study found just 10% of Europe’s billionaires are in finance, and 20% of those in other advanced countries.

Among countries with large financial centers, 19% of U.K. billionaires have made their money through finance, while 25% of those in Singapore and 40% of those in Hong Kong have done the same.

Peterson Institute for International Economics

More broadly, a growing share of the world’s billionaires have made their own money. Just 30% of billionaires in 2014 had inherited their money, compared with 55% in 1996, the study found. One shift over the years in emerging markets: The super-rich are no longer concentrated in the resource and politically-connected sectors of the past but are increasingly company founders.

Looking at riches in a different way, however, and the wealthiest person in each nation tends to have inherited their money, as shown on this map from HowMuch.net: