Mayor Bloomberg is far and away the richest man in town, according to the latest issue of Forbes magazine, beating out the likes of Carl Icahn, Ronald Perelman, and David Koch.

In fact, the publication of the Forbes 400 special issue shows Mr. Bloomberg to be the eighth richest man in America, with a net worth of $20 billion. The ranking also gives the mayor the distinction of posting the most sizable jump in wealth in the past year, rising from no. 25 on the 2007 list, with a net worth of $11.5 billion.

Mr. Bloomberg’s extraordinary rise is tied to his decision to buy back a 20% stake in his eponymous financial data company earlier this year from Merrill Lynch for $4.5 billion, finally settling long-standing speculation as to the value of the private company — and to just how rich he was.

“Until this year, there’d never been a transaction that we could use to pin down the value of Bloomberg LP,” a Forbes editor who oversaw this year’s issue, Matthew Miller, said. “We’ve been conservative when it came to Bloomberg because media companies have consistently been trading down.”

Not all publications have valued Mr. Bloomberg’s company so conservatively: The New York Sun in November 2006 reported that the mayor’s net worth had soared to around $20 billion.

A spokesman for the mayor declined to comment on the publication of the new Forbes ranking.

The Forbes list’s biggest loser is the casino kingpin Sheldon Adelson, who has lost $13 billion over the past year — or, put another way, $1,000 every 2.4 seconds for 12 straight months.

To be sure, the nation’s turbulent economy has provided opportunities for fat profits, and the stories of the richest Americans this year are about being positioned to reap such windfalls. For instance, a New York City hedge fund manager with a net worth of $4.5 billion, John Paulson, accumulated about $3.5 billion of that treasure chest during the past year by accurately forecasting that many Americans would have troubles with their mortgage payments.

New York City resident Philip Falcone, with a $2.5 billion net worth, is new to the Forbes 400 this year after the financier rightly anticipated the subprime credit crisis. His hedge fund boldly shorted subprime credit as well as shares of Bear Stearns, raking in hundreds of millions of dollars when J.P. Morgan bought the troubled investment bank for pennies on the dollar.

Another new addition to the list of richest Americans is the local talk show host Leon Charney, with a net worth of $1.5 billion. “A few Forbes editors had appeared on his show, ‘The Leon Charney Report,'” Mr. Miller said. “Over time we realized he owns more than $1 billion in Times Square real estate.”

Flamboyant real estate mogul Donald Trump remains at the $3 billion mark. “He’s getting good deals and making some impressive developments overseas. The situation here is what’s balancing that out for him,” Mr. Miller said.

A New Yorker also leads the list of most notable drop-offs from the Forbes 400: Maurice “Hank” Greenberg, who built up American International Group over four decades, won’t appear on the Forbes 400 for the first time since 1985.