Bill Gates, Warren Buffet top Forbes list of 400 richest Americans

For the 20th year in a row, Microsoft co-founder Bill Gates has been named the richest person in the United States, according to the Forbes annual list released on Monday.

Gates is worth $72 billion, with Microsoft accounting for only one-fifth of his overall wealth. It turns out most of his money comes from his other investments — notably his firm Cascade, which owns large shares in Deere & Co., the Canadian National Railway and Mexican Coke bottler Femsa.

While the US economy is still battling slow growth, Gates made an additional $9.8 billion in 2013 alone, according to Bloomberg's Billionaire Index.

Warren Buffett, whose net worth is $58.5 billion, ranked number two on the Forbes list.

The 83-year-old CEO of Berkshire Hathaway also made big gains this year, adding another $12.5 billion to his wealth.

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Other big winners include Facebook’s Mark Zuckerberg, whose stock holdings made him $9.6 billion in 2013 and helped him rejoin the top 20 list of richest Americans after getting cut last year.