2009 Revenues: $13.6 billion
The man behind the Gecko runs a big chunk of what Buffett calls Berkshire's growth engine -- insurance. Since 1996, Geico's share of the personal auto insurance market has risen from 2.5% to 8.1%.
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Last updated August 02 2010: 6:54 AM ET
Note: Figures for insurance companies are underwriting revenues.