Mark Zuckerberg became the world’s fourth-richest person on Tuesday, as Facebook Inc. shares fended off plunging stock markets.

The 31-year-old founder of the largest social network had a $50 billion fortune by the close of regular trading in New York. That vaulted him above America Movil SAB’s Carlos Slim and Amazon.com Inc.’s Jeff Bezos on the Bloomberg Billionaires Index, a daily ranking of the world’s 400 richest people.

Even with a 0.4 percent decline for the day, Facebook is up 9.5 percent in 2016, defying gloom across global equity markets. The Menlo Park, California-based company reported results last week that beat analyst estimates, propelling Facebook to the fourth-most valuable company on the planet after Google parent Alphabet Inc., Apple Inc. and Microsoft Corp.

An 18 percent decline this year for Amazon has cut $10.6 billion from Bezos’s fortune, leaving him with $49.1 billion. Bezos was the top-performing billionaire on the index in 2015, more than doubling his net worth. Slim has lost $3.3 billion this year as America Movil takes a hit from the economic crisis in Brazil, the source of 17 percent of its third-quarter sales.

Zuckerberg is the only billionaire among the world’s five- richest people whose fortune has increased this year. Half of the 10 wealthiest billionaires on Earth have made their fortunes in technology.