Facebook founder and CEO Mark Zuckerberg vaulted into elite company when his social networking company's stock made its debut, and the value of his shares made him one of the world's 40 richest people. In the two weeks since Facebook's closely watched May 18 initial public offering, Facebook stock has plummeted, and Zuckerberg has dropped off the list, at least for now. Here, a look at the 28-year-old social media tycoon's roller-coaster finances, by the numbers:

$19.4 billion
Peak of Zuckerberg's fortune, which he hit on May 18, the day of the IPO. Even then, Zuckerberg was worth about a third as much as Mexican billionaire Carlos Slim Helú, the world's richest man.

Price of a Facebook share when trading closed that day

Price of a Facebook share on Wednesday. On Thursday it bounced back to $29.60, after four straight days of losses.

$14.4 billion
Zuckerberg's net worth when the stock hit its low point this week, marking a drop of $5 billion in less than two weeks

Zuckerberg's rank on Bloomberg's Billionaire Index, when his net worth was at its zenith

Rank he held when Facebook stock hit its low point this week

Gap that separated Zuckerberg from Luis Carlos Sarmiento, a septuagenarian Colombian financial tycoon, who was No. 40 on the list on Tuesday, the day Zuckerberg fell out of the top 40

$1.5 billion
Amount Zuckerberg's fortune tumbled on May 25, the worst day of the IPO debacle, when Facebook stock dropped 9.6 percent

$1.1 billion
Amount Zuckerberg pocketed on the day of the IPO, when he sold 30.2 million shares at $37.58 each

503.6 million
Facebook shares Zuckerberg still holds

$104 billion
Value of Facebook based on its stock price at its IPO, which raised $16 billion. It was the first time a company had valued itself above $100 bllion.

$63 billion
The company's valuation two weeks later, a loss of $41 billion

Facebook's price-to-earnings ratio (a measure of how expensive or cheap a stock is) on the day of its IPO, meaning that the stock was priced at 108 times the company's 2011 earnings per share. By contrast, Google's stock sells at about 18 times earnings.

Congressional inquiries launched since the Facebook IPO. Several shareholders who bought stock at the IPO have filed lawsuits against Facebook, its executives, and Morgan Stanley, the IPO's lead underwriter. The angry investors say Facebook should have warned them that analysts at underwriter investment banks had cut their forecasts for Facebook's revenue just before the IPO.

Sources: Associated Press, Bloomberg, Christian Science Monitor (2), CNET, Los Angeles Times, New York Times