THOMAS SIEBEL

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BILLION  SELF-MADE SCORE: * SOURCE: BUSINESS SOFTWARE AGE: 66 RESIDENCE: WOODSIDE, CA PHILANTHROPY SCORE: A former Oracle employee, Siebel made his fortune from software firm Siebel Systems, which he started in 1993 and sold to Oracle for $5.8 billion in 2006. These days he is focused on C3.ai, his AI startup. Before working in tech, Siebel was a cowboy, moving cattle and baling hay at a ranch in Idaho when he was 23 years old. “After graduation I got in a pickup truck and started driving west,” Siebel says. “[I] stopped in Bellevue, Idaho, and was hired on a local ranch as a cowboy.” Today he owns and operates the 71,000 acre Dearborn Ranch in Wolf Creek, Montana.