The Nasdaq 100 Index fell 2.4% on Friday, dragging down the net worth of all 10 of the richest people in the world by at least $1 billion—at least on paper. The index is down more than 10% from its most recent peak.

Tech billionaires alone—who make up many of the world’s richest people—lost $68 billion from their collective fortunes, according to Bloomberg’s calculations. Mark Zuckerberg, Sergey Brin, and Larry Page bid farewell to more than $3 billion each on Friday.

Elon Musk’s net worth dropped from $252 billion on July 31 to $235 billion by Aug. 2, according to Bloomberg’s billionaire index. 

In that time, Oracle’s Larry Ellison briefly saw his wealth balloon by $3 billion on paper overnight before losing all his gains and a further $3 billion the following day.

Meanwhile, when Amazon shares dropped by nearly 9% in one day on August 2, its founder Jeff Bezos saw nearly $16 billion wiped from his wealth.

Notably, this is the third-worst wipeout for Bezos, as he previously lost $36 billion in April 2019 following his divorce settlement. His net worth now stands at around $191 billion.

The world’s second-richest person has also been steadily offloading Amazon shares this year. The 60-year-old sold about $8.5 billion worth of stock over nine trading days in February, before recently revealing his plan to sell 25 million additional shares worth $5 billion.

Why have U.S. tech stocks tumbled?

In short, uncertainty over AI, Federal Reserve rate cuts, and a potential recession, as well as some high-profile earnings disappointments, have helped plunge the tech-heavy index into correction territory.

The downturn began when Amazon announced on an earnings call that profit will take a back seat as it plans to invest heavily in AI. This made investors worry about AI gains being overhyped and led to the biggest decline in Amazon shares since April 2022 when they plunged by 14%.

At the same time, Microsoft posted slowing growth in its Azure cloud-computing arm and said it expected to keep spending heavily on data centers. Meanwhile, Tesla missed earnings estimates for the second quarter, and Alphabet’s YouTube ad revenue fell short of expectations.

What’s more, a report from the Labor Department indicated the U.S. economy added around 61,000 fewer jobs last month than expected. 

Plus, with unemployment at 4.3%—the highest since October 2021—concerns of a looming recession are getting louder.