The exclusive group of the world's richest people continues to grow in members and wealth, with former Mayor Michael Bloomberg adding $6 billion to his fortune.

Leaving behind his title of richest mayor in December, Bloomberg ranked 16th on the latest Forbes ranking, with a net worth of $33 billion.

"Bloomberg's net worth is pretty much tied up in the company he created, Bloomberg LP," said Kerry Dolan, Forbes' assistant managing editor. "It's not growing at the rate it once was, but it's still doing well."

Of the 1,645 billionaires around the globe, 71 reside in New York City, second only to Moscow, with 88.

Meanwhile, Bill Gates climbed back to the No. 1 spot as the world's wealthiest person after a four-year hiatus. The Microsoft founder had a net worth of $76 billion, up from $67 billion last year. Gates held the wealth title for 15 of the last 20 years and he beat out telecom tycoon Carlos Slim Helu of Mexico, worth $72 billion, this year.

"It's an incredibly successful set of entrepreneurs operating all over the world and employing huge amounts of people," Dolan said.

The group's total net worth equals $6.4 trillion.