(Reuters) - Market turmoil has put a dent in the bank accounts and portfolios of the world's richest people.

Forbes magazine has crunched the numbers for its annual billionaires' list, revealing a drop in average net worth for the first time since 2010.

Holding on to the top spot is Bill Gates.

The Microsoft founder takes the crown for the 17th time, even though his wealth dropped more than US$4 billion (S$5.56 billion) from last year.

He's followed by Spanish retail giant Amancio Ortega, the man behind fashion chain Zara.

The Oracle of Omaha, Warren Buffett, saw his wealth plummet nearly US$12 billion, but he still takes third place.

Mexican telecom tycoon Carlos Slim falls two spots to number four, as shares in his company tumbled.

And Amazon.com CEO Jeff Bezos makes his debut in the top five.

Forbes says Facebook's Mark Zuckerberg made the biggest gains, adding US$11 billion to his fortune.

While the richest woman in the world remains L'Oreal heiress Liliane Bettencourt.