Why do aerospace engineering professors make a little more money than classics professors at some public universities, and a whole lot more at others?

The answer, according to a study by the Cornell Higher Education Research Institute, to be published in the Economics of Education Review, is that faculty members in departments that are perceived as being higher quality get paid more.

The researchers looked at 1992-3 salary data from 88 institutions, 85 of which are public, many of them flagships or other research insitutions. The researchers already knew that computer science teachers at a given institution make more than philosophy instructors, but what they found was that the relative spreads between any two particular disciplines were widely variable at different universities. The study found a correlation between department quality as determined by National Research Council ratings, and the relative pay of faculty members in different disciplines.

For example, if a college’s economics department was rated well and its English department only average, the salary gap between economics and English faculty members at that institution was likely to be larger than the gap at an institution where both were rated equally.

The question then becomes: Is higher pay used to attract better faculty members, or do institutions shell out more cash to current faculty members when they see a department doing well? It could be either in a particular case, but the researchers said salary differences don’t necessarily tell a university it should redistribute its money. "Engineers at one college might say, ‘We only make 20 percent more than English faculty here, and the average for an institution is 40 percent,’ ” said Ronald Ehrenberg, director of the institute and lead author of the study.

Ehrenberg said that faculty salaries essentially express the preferences of a university, and different universities prefer strength in different areas. “Universities have to know what’s important to them, and they give weight to different disciplines. That comes from the nature of the university, and where they are historically strong.”

Another result of the study was that these relative salary gaps among institutions have widened over the last decade, and are even wider today for junior faculty members than for senior faculty members. Ehrenberg thinks that is because the marketplace is saturated with high paying jobs for economists, engineers, and computer scientists, and not for humanities professors. In order to keep their top faculty members, institutions are forced to compete with salaries available in the private sector. “It’s a difficult issue,” Ehrenberg said. “If it were to continue, it runs the risk of causing a tremendous loss of collegiality as relative salary differentials get wider.”

Some experts thing colleges should resist these trends. “Even within a single college, differences are growing, and that creates some difficulties for faculty to see themselves as part of a common profession,” said John Curtis, director of research for the American Association of University Professors. “Higher education really is something for the common good that provides a benefit for society as whole. When you see some of these large differences, it’s easy to slip into a system that emphasizes individual payback instead of payback for society.”

So what is an institution to do? Curtis thinks higher education would have to break free of some of the influence of the marketplace. “Part of the answer is to make sure disciplines where there isn’t so much of a ‘market’ for the faculty are also getting support,” he said. “As public support declines, institutions become more driven by the outside market.” And he does not think the market will do good things for education. “If we move to a more corporate structure, then there’s an idea of ownership of data or information, and of limited exchange, and that, in the long run, will damage the whole enterprise.”