Via a mailing list, probably via this Tyler Cowen post, an awful statistic about adjunct faculty:

35 years ago there were 44% more tenured faculty than adjuncts. Today there are 76% more adjuncts than tenured faculty, via @chronicle

— Ángel Cabrera (@CabreraAngel) April 25, 2014

This is awful in two ways. First, it’s obviously a sad comment on the state of the college teaching profession. More importantly, though, it’s a classic abuse of statistics, using a really confusing presentation of the numbers to exaggerate an effect that doesn’t really need it.

Here, let’s try this as a poll, since the way this is stated basically amounts to an eighth-grade algebra word problem. Answer before scrolling down to read the explanation:

(A 10-percentage-point increase here means going from, say, 12% to 22% of the total. Which is not the right answer, by the way.)

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If you want numbers to make a sensible comparison, you have to solve some equations– if we say that the number of adjunct faculty 35 years ago is x, then the number of tenure-track faculty is 1.44x, and the fraction of adjunct faculty is:

The modern calculation has the number of tenure-track faculty as y and the number of adjuncts as 1.76y, so:

In other words, according to these poorly sourced statistics (I didn’t turn this up on the Chronicle of Higher Ed site or Twitter feed), the adjunct fraction increased from 41% to 64%. It ought to be enough to note that adjuncts have gone from a sizable minority of faculty to a substantial majority, but the “X% more than” formulation is just confusing, in order to sound more scary. Nobody reports numbers this way unless they’re engaged in “How to Lie With Statistics” hackery.

No matter how good the cause, responsible academics should be better than this.