“Public colleges and universities, reeling from immediate and long-term cutbacks in their state funding, have sought to reduce spending on the back of their students, increasingly substituting lower-paid contingent faculty members for more fairly paid tenure-track faculty members,” the report said.

The concentration of contingent faculty “weakens the academic enterprise,” the report said.

“The problem is not the people who are in the part-time or nontenure positions, it’s the lack of support they get from their institutions,” said John Curtis, the director of research and policy at the association. “With so many contingent faculty, students may not be able to develop a relationship with their professors, who may have no office, no university e-mail, and may not even be listed in the directory. There was a report titled ‘Who is Professor ‘Staff’ and How Can This Person Teach So Many Classes?’ which really sums it up.”

And because contingent faculty have no job security, he said, they can lose their job if they are critical of their institutions or stir controversy in the classroom.

Along with the data on full-time professors’ pay that the association collects from colleges and universities each year, this year’s report includes data from a Coalition on the Academic Workforce survey of more than 10,000 part-time faculty members, finding that their median pay per course in 2010 was $2,700. Generally, private nonprofit institutions paid more than public ones, and doctoral universities more than baccalaureate or community colleges — and for-profit colleges paid only half to two-thirds as much.

Terry Hartle, senior vice president of the American Council on Education, said that while the shift to contingent faculty was an inexorable fact of life, he was not convinced that it harmed the quality of education — and he added that it might even improve quality in some vocational programs. The trend is likely to continue, he said.