47. Thomas Siebel

Siebel Systems founder

2003-07 Given or Pledged: $189 million
Favored Causes: Education, meth-use prevention, community
Estimated Lifetime Giving*: $386 million
Net Worth**: $1,900 million
Giving as a Percentage of Net Worth: 20%

To kick off the fund-raising efforts of his alma mater, the University of Illinois, Siebel donated $100 million dollars to the school. In 2005, he founded the Meth Project, a prevention program aimed at significantly reducing first-time methamphetamine use through public service messaging, public policy, and community outreach. The Meth Project operates statewide prevention programs in Arizona, Idaho, and Montana, and hopes to branch into more states in upcoming years.

*Based on public records and interviews with donors
**Based on the Forbes 400 list and donor information
Data: BusinessWeek, GuideStar, The Chronicle of Philanthropy, The Center on Philanthropy at Indiana University