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Ajit Jain
Company: Berkshire Reinsurance
2009 Revenues: $6.7 billion

Jain took over Berkshire's tiny reinsurance business in 1985 and turned it into a powerhouse. As Buffett once wrote, "If Charlie, I, and Ajit are ever in a sinking boat -- and you can only save one of us -- swim to Ajit."

NEXT: Tad Montross

Last updated August 02 2010: 6:54 AM ET
Note: Figures for insurance companies are underwriting revenues.
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