#10: New York City Mayor Michael Bloomberg, $25 billion // Financial data services firm Bloomberg LP

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#9: S. Robson Walton, $26.1 billion // Walmart

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#8: Alice Walton, $26.3 billion // Walmart

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#7: Jim Walton, $26.8 billion // Walmart

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#6: Christy Walton and family, $27.9 billion // Walmart

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#5: David Koch, $31 billion // Co-owner of Koch Industries Inc.

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#4: Charles Koch, $31 billion // Co-owner of Koch Industries Inc.

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#3: Larry Ellison, $41 billion // Oracle Corp. co-founder

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#2: Warren Buffett, $46 billion // Head of Berkshire Hathaway Inc.

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#1: Bill Gates, $66 billion // Microsoft Corp. co-founder

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