Gates, Buffett top Forbes 400 ranking of richest Americans

Microsoft co-founder Bill Gates remains the richest American with estimated assets of $54 billion, according to Forbes magazine's annual ranking of the 400 richest Americans.

Warren Buffett, CEO of Berkshire Hathaway, ranks second in the U.S. with $45 billion. It's a repeat performance, as Gates, 54, and Buffett, 80, were Nos. 1 and 2 last year.

The wealth of 85 list members declined this year from 314 in 2009, while wealth increased for 217 members. The total worth of the 400 rose by 8% to $1.37 trillion, still below the 2008 total of $1.57 trillion.

Facebook CEO Mark Zuckerberg, 26, is tied for No. 35 on the list and saw his wealth jump 245% to $6.9 billion, the largest percentage increase of anyone on the list.

Sixteen new people joined the list this year, including Dustin Moskovitz, a co-founder of Facebook who left the social networking site in 2008. He has a net worth of $1.4 billion, tying him for No. 290. Moskovitz, 26, is the youngest person on the list. The oldest is philanthropist David Rockefeller Sr., 95, who is tied for No. 153 with $2.4 billion.

There are 42 women on the list, led by Christy Walton, 55, at No. 4 and 60-year-old Alice Walton at No. 8, of the family that controls Wal-Mart. Jim Walton ranks no. 7 with $20.1 billion and S. Robson Walton is No. 9 with $19.7 billion.

New York City Mayor Michael Bloomberg, 68, is ranked 10th with $18 billion.

The other members in the top 10 are Oracle CEO Larry Ellison, 66, at No. 3 with $27 billion. Charles Koch, 74, CEO and chairman of Koch Industries tied for fifth with his brother David Koch, 70, with $21.5 billion.

California has the most super-rich people with 83, followed by New York with 64. Texas has 45 members and Florida has 26.

The cutoff for the Forbes 400 list is back up to $1 billion after falling to $950 million last year.