Questions about how much U.S. grantmaking foundations spend on staff, trustees, overhead, and other administrative expenses—and how much is appropriate to spend—are at the forefront of current debates on foundation practices. This report provides a comprehensive look at expense and compensation patterns of the 10,000 largest independent, corporate, and community foundations (by giving) and documents how major differences in foundations' operating characteristics have an impact on their expense levels. The findings shed light on what factors are tending to drive administrative and operating expenses. Understanding foundations' program strategies and characteristics are key to understanding how much they spend.