Plunging stock markets are exacting a toll on the world’s biggest fortunes.

The 400 richest people have lost $305 billion from their combined net worth this month as global equities tumbled for the worst start to a year on record as concern mounts that global growth is faltering.

The billionaires lost more than $115 billion this week, with 76 taking hits of at least $1 billion in January, according to the Bloomberg Billionaires Index. Seven shed more than $1 billion on Friday alone as the Dow Jones Industrial Average sank 391 points, European stocks fell into a bear market and the Shanghai Composite Index wiped out gains from an unprecedented state-rescue campaign.

Amazon.com Inc. founder Jeff Bezos led decliners on the Bloomberg index, losing $8.9 billion since Jan. 1 and $1.9 billion Friday when the Internet retailer declined 3.85 percent. Bill Gates, the world’s richest person, has lost $6.8 billion of his net worth this year and Wang Jianlin, China’s richest person, is down $6.4 billion.

The combined net worth of the 400 billionaires is $3.6 trillion, a 16 percent decline from their peak of $4.3 billion on May 18, 2015.