Thanks to a nearly 30 per cent leap in the company's stock price Thursday, Bloomberg News estimates Zuckerberg's fortune swelled by US$3.8 billion, which coincidentally is the same amount that AT&T (T) reported in net income in its most recent quarter and the size of Philadelphia's budget.
Keep in mind that figure is based on Thursday's jump in Facebook's stock, and many Wall Street analysts believe the shares have more room to run.
Zuckerberg, 29, has eclipsed Microsoft (MSFT) co-founder Bill Gates, 57, and Dell (DELL) founder Michael Dell, 48, on the Bloomberg Billionaires Index. (Microsoft owns and publishes MSN Money.) He now ranks 42nd, with a net worth of $16.8 billion. Zuck's fortune is up by 37 per cent so far this year.
That's not too shabby for someone whose company was written off as irrelevant as recently as a few months ago.
Zuckerberg and his wife, Priscilla, have said they'll donate most of their fortune to charity. In 2011, he pledged $100 million to the Newark, N.J., school system. And the Silicon Valley Community Foundation got almost $500 million in Facebook stock from the billionaire in December.
Jonathan Berr does not own shares of the listed stocks. Follow him on Twitter @jdberr.
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