It's a number on the order of 10 percent. The larger trouble is that as the faculty ages, some universities are likely to find themselves with a growing pool of professors over 70. But by 1996, only about 30 percent of the professors at 70 were opting to retire. While age is not usually a determinant of competence, Mr. Hamermesh, the Texas economics professor, thinks that some professors don't always know when to call it quits. Examining their student evaluations, she found that in half of the courses, there was no difference in how the two professors were rated.
People lose it at a certain age.
They don't all lose it. But when you lose it, you really lose it. As was predicted before the end of mandatory retirement, top research universities are the most likely to see lots of professors stay on past 70. Universities don't want these faculty to go away. They would just like them to stop getting paid.