NEW YORK (BLOOMBERG, REUTERS) - Facebook chief executive Mark Zuckerberg's fortune took an almost US$16 billion (S$21.8 billion) hit on Thursday (July 26), as the social media giant suffered the biggest one-day wipeout in US stock market history, a day after executives forecast years of lower profit margins.

The loss is the biggest one-day wipeout of individual wealth ever recorded on the Bloomberg Billionaires Index ranking, which started tracking the world's biggest fortunes in 2012.

Zuckerberg lost more wealth in a single day than the entire market value of Nasdaq or Ralph Lauren.

In fact, about 175 companies in the S&P 500 are worth less than the US$15.9 billion that vanished from the fortune of the Facebook co-founder as shares of the social media giant plunged 19 per cent on Thursday.

Zuckerberg, 34, is now the world's sixth-richest person, with US$70.6 billion, down three rungs on the Bloomberg Billionaires Index.

Other big Facebook investors also took a hit as disappointing second-quarter results obliterated US$119 billion of market value, the most ever in a day for a US company.

Co-founders Dustin Moskovitz and Eduardo Saverin lost US$3.9 billion and US$2.2 billion, respectively, while chief operating officer Sheryl Sandberg lost US$100 million.