Mondays are the worst. As proof, here’s how Forbes tracked how these six billionaires lost $18.8 billion at the end of the day’s market plunge, when the Dow Jones Industrial Average dropped 1,175 points, or 4.6%. It’s the largest one-day drop the index’s history as it lost its gains for the year.
(Of course, last Friday wasn’t great, either. The weekend kicked off with the world’s 500 richest people losing $68.5 billion.)

Warren Buffett: $5.3 billion

The Oracle of Omaha lost 6% of his net worth but is still the world’s third-richest person with $84.6 billion*. The 87-year-old Berkshire Hathaway Inc. chairman is the biggest shareholder of Wells Fargo & Co., which Bloomberg notes led the S&P 500’s losses with 9.2%.

Mark Zuckerberg: $3.6 billion

Facebook’s CEO saw 4.7% of his fortune vanish as shares of his social media company fell 5% (but he’s still worth $73.1B).

Jeff Bezos: $3.2 billion

He remains the planet’s richest person (he became $28 billion richer over the past four months as Amazon shares surged up 30%), but Monday erased the same $3.2B he gained in a day last week after Amazon announced quarterly results. His new balance of $115.7 billion still puts him $25 billion ahead of Microsoft’s Bill Gates, the world’s No. 2 richest person.

Larry Page, Sergey Brin, Larry Ellison: $2.2 billion each

Google cofounders Page and Brin shared the pain as shares of parent company Alphabet fell 5%. Ellison is the founder of Oracle.
*Source: Forbes real-time billionaire rankings