WhatsApp CEO Jan Koum has been cashing out his Facebook stock at a rapid pace.

Koum, who sold WhatsApp to Facebook for $19 billion back in early 2014, sold and gifted almost 43 million shares of Facebook stock in the past calendar year, according to a review of his Securities and Exchange Commission filings.

Those shares, based on Facebook’s stock value on the dates of the sales, would be worth more than $5 billion.

Most of these shares were sold. Filings show that Koum made more than 120 separate sale transactions since April 1, 2016, selling more than 30 million shares of stock for about $3.7 billion.

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He also gifted 12.6 million shares, according to filings, though the filings did not specify where the gifts were headed. All of the sales were done using a 10b5-1 trading plan, which executives use to sell shares while avoiding concerns over inside trading.

It’s not uncommon for executives to sell their stock — company stock awards and options usually represent the vast majority of executive compensation.

It is uncommon for executives to sell as frequently as Koum has, though, unloading more than half of his Facebook holdings. According to Facebook’s annual proxy, which was filed Friday, Koum went from owning 2.6 percent of all of Facebook’s Class A common stock to just 1.2 percent in the past year.

We reached out to WhatsApp to ask for comment. Maybe Koum is building a space craft or something cool? Or maybe his wallpaper is made out of $100 bills? We’ll let you know if we hear back.

Either way, Koum is not the only Facebooker who sold a lot of stock last year. CEO Mark Zuckerberg also sold more than $1 billion worth of stock, but this was to fund his philanthropic efforts through the Chan Zuckerberg Initiative.

By Kurt Wagner, Re/code.net.

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