- The 14% rise in Facebook stock this year has bolstered Zuckerberg's fortune, while the 23% decline in Berkshire stock has hammered Buffett's wealth.
- Another factor is that Buffett gave $15 billion to charity between 2014 and 2018, dwarfing the $1 billion given by Zuckerberg and his wife over the same period.
- However, Zuckerberg should catch up to Buffett eventually as both plan to give the vast majority of their fortunes to charity,
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Facebook CEO Mark Zuckerberg blew past Berkshire Hathaway CEO Warren Buffett in net worth last week. The $20 billion difference in their fortunes isn't just a product of Facebook stock outperforming Berkshire stock; it also reflects Buffett giving far more than Zuckerberg to charity.
Buffett's net worth has plunged by more than $20 billion this year to about $69 billion, while Zuckerberg's wealth has swelled by about $11 billion to north of $89 billion, according to the Bloomberg Billionaires Index .
Read More: Jefferies breaks down the top 22 stocks it thinks you should buy right now including 6 fast-risers that just captured its attention Their fortunes are closely tied to their respective companies' stock prices: Buffett owns about 16% of Berkshire, while Zuckerberg owns 13% of Facebook. The roughly 23% slump in Berkshire shares since January has hammered Buffett's net worth, while the 14% surge in Facebook stock has boosted Zuckerberg's net worth over the same period. However, the scale of their philanthropy is another big factor. Buffett gave nearly $15 billion to charity between 2014 and 2018, dwarfing the $1 billion given by Zuckerberg and his wife, Priscilla Chan, according to a list of America's 25 biggest givers compiled by Forbes and SHOOK Research. There would be a much smaller gap in their net worths without those donations. Buffett would be worth about $84 billion, while Zuckerberg would be worth about $90 billion. Read More: The world's biggest investors are notoriously skeptical of the stock market's bet for a quick economic recovery and warning that the 'fantasy' rally will soon come crashing down It's worth noting their philanthropy gap is set to close in time, as both Buffett and Zuckerberg plan to give away almost all of their money. "More than 99% of my wealth will go to philanthropy during my lifetime or at death," Buffett vowed as part of The Giving Pledge , an initiative he launched with Bill and Melinda Gates in 2006 to encourage billionaires to give away the majority of their fortunes. "We will give 99% of our Facebook shares currently about $45 billion during our lives to advance this mission," Zuckerberg and Chan said in a public letter to their newborn daughter in 2015. The pair signed The Giving Pledge five years earlier , in 2010. Here's a chart showing how Facebook rapidly caught up to Berkshire Hathaway in market capitalization, and eventually surpassed it, after going public in May 2012: Business Insider NOW WATCH: A cleaning expert reveals her 3-step method for cleaning your entire home quickly See Also: WeWork could falter as costs spiral and social distancing hits offices, the boss of a rival real-estate group said 10 big-money investors each share the single market risk they think traders are overlooking right now The investment chief of a $12 billion wealth-management firm breaks down how to build the perfect portfolio using just 7 ETFs one designed to sidestep a dramatically 'overvalued' stock market