20. Klaus Tschira
Net worth: $8.6 billion.
The 74-year-old Klaus Tschira left IBM with four of his colleagues in 1972 and together founded SAP (Systems, Applications, Products). It later went public in 1988 and has since become a market leader in the B2B space in the areas of enterprise and mobility applications, analytics, databases, cloud computing services and more. SAP has more than 74,000 employees and has an annual revenue of over $20 billion.
The German born Tschira retired in 1998 and left the supervisory board in 2007 but started a charitable foundation, which holds SAP shares. Forbes said his charity is one Germany's largest philanthropic organizations and has provided over $350 million in funding and in-kind donations to promote science, mathematics and computer science in schools and extracurricular settings.
Tschira has taken up astronomy as a hobby and has an asteroid between Mars and Jupiter named after him. Forbes ranks Tschira as the 153rd richest person in the world.