Facebook's 2017 stock surge has Mark Zuckerberg keeping some much-older company.
With up nearly 50 percent this year, the company's co-founder and CEO is now the world's fifth-richest person, thanks to a fortune worth roughly $70 billion.
That puts Zuckerberg, 33, between Mexican telecom mogul Carlos Slim Helu, 77, and billionaire U.S. investor Warren Buffett, age 86, according to a list of the world's richest compiled by Forbes.
And those aren't the only senior citizens whom Zuckerberg now calls peers.
The average age of the 10 wealthiest individuals is 72.7 years old, excluding Zuckerberg. Even including him, the average is still 68.7, or more than double his age.
He's the only member of the top 10 list below the age of 50. Amazon CEO Jeff Bezos is next closest at 53.
And among the 20 richest, he's the only member of the list below age 40.
Indeed, among those who have enough hair to judge, Zuckerberg is the only one of the world's 12 richest people not to have a head full of gray (Bezos' bald pate making his current color difficult to ascertain.)
As of March 31, 2017, Zuckerberg owned 410,758,857 Class B Facebook shares, or a whopping 77 percent of the total, according to page 37 of the company's annual proxy filing.
At Monday's closing price of $169.25, those shares — which control most of the company's voting rights, and thus the company — are worth approximately $69.5 billion.
Zuckerberg then owned a much smaller number of Class A shares, now worth roughly $445 million, the filing says. (The company also has a third class of shares, Class C, that have no voting rights.)
Since then he has continued to sell off his holdings at regular intervals. In July, for example, Zuckerberg sold $42.5 million worth of Class A stock via more than a dozen transactions.