One of the many things University of Toronto Prof. Jordan Peterson (pictured above) and TV interviewer Cathy Newman talked about recently in their now-famous-on-YouTube discussion on Britain’s Channel 4 was the male-female wage gap.

Peterson explained that when you do multivariate econometrics, it’s not clear there is a wage gap—it largely disappears when the influence of relevant variables is considered. Newman either didn’t believe that or didn’t understand the point Peterson was making but instead kept trying to get him to agree that the wage gap was a problem. Peterson didn’t budge, as he almost never does, which is what makes him so unusual in this age of obligatory diversity in all things except acceptable thought.

It’s hard to fault Newman for not getting or agreeing with the point, though. Most people don’t. But here’s another unexplained wage gap that may help.

Barnard College Prof. Daniel Hamermesh, one of the world’s leading labour economists, just published a paper pointing out that, on average, U.S. professors make 15 per cent less than other Americans with the same advanced degrees. Hamermesh does understand that sympathy for professors is likely to be limited. They may make less than similarly-qualified non-professors but they nevertheless make 44 per cent more than people the same age who work the same hours but don’t have advanced degrees.

So he calls his paper Why are professors "poorly paid?"—with air quotes.

All sorts of reasons come to mind as to why professors might be paid less than other PhDs or MAs. Professing is a unique type of work. Universities and colleges are unique places to work. Many professors get tenure, which means they can only be fired for cause after due process (in theory, at least, though standards on such matters, especially where sexual impropriety is alleged, are changing rapidly). Given those differences and many more one could think of, the existence of a wage gap wouldn’t necessarily be surprising.

Is it possible to explain the gap statistically, as people have done with the male-female wage gap?

Ideally, you’d like to include all the attributes of academic and non-academic jobs, and the personal characteristics of the people whose wages you’re looking at. Not surprisingly, data that rich simply doesn’t exist. In its absence, Hamermesh tries a couple of things to see to what extent the vaunted and, in my own experience, actual flexibility of professorial work might be a reason academics are willing to work for less money.

As it turns out, there are detailed surveys of how people spend their time. On average in the United States, academics work 45.17 hours a week, which is a little less than other holders of doctorates, but only a little. Non-academic PhDs work 45.38 hours a week. Academics have more flexibility in how they work, however—22.7 per cent of them work in the evening, compared to 19.3 per cent of other doctorates, while 27.8 per cent of them are real night owls, working from 10 p.m. to 6 a.m. vs. only 20.2 per cent of other doctorates doing that.

Academics also tend to work more on the weekend: 5.5 hours on average vs “only” 3.9 hours for other doctorates. And, not surprisingly, academics work less during the summer, averaging just 38.9 hours a week from June to August, compared to other doctorates, who average 43.2 hours, just a little more than two hours less than their non-summer average.

So there’s a difference between academic and non-academic PhDs in how much they time-shift. But it’s hardly a gigantic difference. Could it really explain a 15 per cent wage gap? Hamermesh argues that if you plug the differences into a standard “utility function” and apply reasonable assumptions about trade-offs, the most you can explain is about a third of the gap.

To confirm that flexible scheduling does matter to academics, Hamermesh did his own survey of labour economists—who admittedly aren’t a random sample of academics—asking them what are the top three things they like about their jobs.

“Schedule freedom” was mentioned by 40 per cent of his 289 respondents. But that placed it only fourth on the list of job features, behind: the freedom and novelty of research, which almost 90 per cent valued; teaching and working with students, which about 75 per cent mentioned; and interactions with colleagues, which appealed to about 45 per cent of respondents. (The ability to travel and be one’s own boss was put in the top three by 15 per cent of respondents while, something of interest to Fraser Institute readers, having an impact on policy, was top-three for less than 10 per cent of respondents.)

Professors as a group obviously aren’t the same as women as a group (though the groups do overlap; Hamermesh doesn’t say how many of his respondents were women, although in 2016/17, 40.2 per cent of Canadian professors were, according to StatsCan). But professors apparently also experience an unexplained pay gap.

Best try to explain it before deciding it’s discriminatory.