No. 11: John and Laura Arnold

Amount donated in 2014: $218.4-million

Main beneficiary: Laura and John Arnold Foundation

Background: Mr. Arnold founded Centaurus Energy, a hedge fund. Ms. Arnold is a former corporate lawyer.

Houston philanthropists John and Laura Arnold gave nearly $108-million to their Laura and John Arnold Foundation, which supports programs to improve the reliability of scientific research, K-12 public education, the criminal-justice system, and public-policy practices.

The foundation awarded a total of nearly $108.3-million last year, including a $5.7-million grant to the Center for Healthcare Transparency; a nearly $10-million grant to Harvard University to establish its Harvard Health Care Markets and Regulations Lab; and a $9.4-million award to William Marsh Rice University for its OpenStax program, which aims to develop digital tools to replace printed textbooks in K-12 public schools.

The Arnolds, who are in their early 40s, also gave a total of $110.5-million to a variety of education groups, nonprofits that work in the criminal-justice system, public-accountability organizations, and others throughout the country.