https://www.cnbc.com/2017/09/22/mark-zuckerberg-selling-up-to-75-million-facebook-shares.html

Mark Zuckerberg will sell a large number of Facebook shares over the next 18 months in sales that would be worth between $6 billion and $12.8 billion based on the stock's current price.

The intention to sell between 35 million and 75 million shares was disclosed in a Facebook securities filing late Friday.