In the wake of a tumultuous time for the stock market and also for Facebook, CEO Mark Zuckerberg is on track to end 2018 down the most money of any billionaire. Zuckerberg has lost $19.8 billion year to date, according to Bloomberg.

With a current net worth of $52.9 billion, Zuckerberg ranks seventh on Bloomberg's Billionaires Index, a daily ranking of the world's richest people that is updated at the close of every trading day in New York. On Jan. 1, Zuckerberg had a total net worth of $72.8 billion, according to Bloomberg historical data; that's a 27.3 percent loss year to date.

With just over a week left in 2018 and Facebook backlash continuing to affect its stock, Zuckerberg (who owns about 13 percent of the company, which makes up much of his net worth) could finish the year as the biggest billionaire loser, as Money points out. In fact, Zuckerberg's nearly $20 billion loss is almost equivalent to Tesla CEO Elon Musk's entire fortune ($23.4 billion, according to Bloomberg).

On July 25, 2018, Zuckerberg's net worth was at its high point for the year, $86.5 billion, according to Bloomberg's historical data.

There are currently many billionaires down year to date (as of Dec. 20 close Bill Gates is down $1.6 billion and his buddy Warren Buffett is down $5.8 billion, according to Bloomberg).

However, one big-name billionaire is having a better year. The richest person in the world, Amazon founder and CEO Jeff Bezos, is up $22.7 billion year to date, with a current net worth of $122 billion, according to Bloomberg. However that's still down from his 2018 net worth high of $168 billion in September, according to Bloomberg historical data.

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