Following Facebook's astonishing fall in market value on Wednesday , CEO Mark Zuckerberg is at risk of losing third place on Bloomberg's Billionaires Index .

The social network's value plunged nearly 24% after its disappointing Q2 earnings report and executives (including Zuckerberg) warning of slowing revenue growth. Shares recovered slightly, closing after-hours trading down 20.2% at $217.50.

Bloomberg reports that Zuckerberg's fortune took a hit of $16.8 billion as a result, and that if Facebook's drop in value holds through to end of trading on Thursday, then he will slip down its Billionaires Index by three places.

Zuckerberg is currently worth $86.5 billion, but the loss would push him under the $70 billion mark. This would mean he drops from number three to number six, putting him behind Amancio Ortega, the founder of retail chain Zara. The loss would also negate his $13.7 billion of gains for the year.