The collective wealth of the world’s billionaires rose by 17% in 2016 to US$6 trillion after falling the year before, according to the UBS/PwC Billionaires Report 2017 published Thursday.

The report finds that the total wealth of the world’s richest people grew at about double the rate of global stock markets in 2016, as tracked by the MSCI World Index.

The report shows that Asia’s wealthy led the way, and the region’s billionaires now outnumber their American counterparts for the first time.

“This year we have seen not only a return to growth for billionaire wealth, but also a significant shift in its geographic dimensions. Dramatic growth in Asian wealth shows it could overtake the U.S. in just four years,” says Josef Stadler, head global ultra high net worth at UBS AG, in a statement.

In total, there are 1,542 billionaires in the world, according to the report. The total number of Asian billionaires rose by almost 25% in 2016 to 637, compared to 563 in the U.S. and the combined wealth of Asian billionaires also grew by almost 33% from US$2.0 trillion.

Still, the U.S. maintains the largest concentration of billionaire wealth, with a combined US$2.8 trillion, driven by American billionaires’ involvement in tech, financial services, and materials, the report notes.

In Europe, the population of billionaires largely held steady in 2016; their collective wealth grew by 5% to just over $1.3 trillion.

“Billionaires are also having a wider impact on the global economy through the people they employ and the growth they foster,” adds Stadler. “The societal effect of great wealth is, however, not exclusively economic. Through their own passion for arts and sports, they are playing an increasingly important role in enriching the cultural life of communities.”

For insights on helping affluent clients, read HNW Guide 2017, IE’s first guide to serving the needs of high net-worth clients, from getting into their mindset to developing the top level service they demand.