Over the last two decades, colleges and universities doubled their full-time support staff while enrollment increased only 40 percent, according to a new analysis of government data by the Center for College Affordability and Productivity, a nonprofit research center.

During the same period, the staff of full-time instructors, or equivalent personnel, rose about 50 percent, while the number of managers increased slightly more than 50 percent.

The data, based on United States Department of Education filings from more than 2,782 colleges, come from 1987 to 2007, before the current recession prompted many colleges to freeze their hiring.

Neither the report nor outside experts on college affordability went so far as to argue that the increase in support staff was directly responsible for spiraling tuition. Most experts say that the largest driver of tuition increases has been the decline in state financing for higher education.