Mark Zuckerberg's stake in Facebook has been reduced to just under 20%, according to an SEC filing on Friday.
Zuckerberg, the company's cofounder and CEO, now owns 478.9 million shares of Facebook, or 19.6% of all shares. One year ago, Zuckerberg's stake in the company was nearly 30%.
See also: Is Facebook Too Big to Fail?
In December, Zuckerberg sold $2.3 billion worth of Facebook, largely to pay his tax bills for options that he exercised.
Zuckerberg famously pledged in September 2012 not to sell any shares of Facebook for at least a year, a move that was intended to show his confidence in the stock at a time when it had hit a new low. A few months later, he actually increased his stake in the company to 29.3% from 28.2% on the day of the IPO.
Facebook's stock doubled throughout 2013, driven by renewed optimism for the social network's ability to make the shift to mobile. As a result, Zuckerberg's net worth increased by $12.4 billion for the year, more than any other current tech exec, excluding Microsoft founder Bill Gates.
Facebook stock was up a little more than 3% in morning trading Friday following the news.
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