Brad Weiner, Dean of the College of Natural Sciences at the University of Puerto Rico Rio Piedras, has a new blogpost up at Huffington Post attacking the UPR student strikers and defending the decision to bring police onto campus. There’s already a vigorous debate over his claims beginning to heat up in comments to his post, but there’s one piece of his argument that’s worth looking at in detail.

Weiner writes:

Many of the recent UPR student conflicts have received national and even international attention. As a result, my stateside colleagues invariably have many questions. I always try to carefully explain the issues. Inevitably, I get the following question: “How much do students at the University of Puerto Rico pay for tuition and fees?” My answer: $1200-$1500, depending on the number of credits. Per semester? No, per year. At that point, the discussion usually ends in disbelief because they cannot believe (1) how low the tuition and fees are, and (2) how it possibly can be an issue, given the cost of higher education everywhere else, including other institutions in Puerto Rico.

But tuition isn’t the only cost of attending a university — there are mandatory fees to be paid as well. And according to the Chronicle of Higher Education, in-state tuition and fees at UPR Rio Piedras last year were actually $1,814, not “$1200-$1500.”

That’s still pretty good, though, right? Well, sort of. Because as Weiner surely knows — but many of his stateside colleagues presumably do not — income in Puerto Rico lags far behind that of households in the continental United States. According to the census bureau, in fact, median household income there is only $17,500 — less than 35% of the national average of $50,221.

The national average tuition and fees at four-year public colleges, according to the Chronicle, is $6,633. That means that UPR’s planned $800 a year tuition hike would push UPR tuition up to 104% of the income-adjusted national average, and it would do so by hiking tuition the stateside equivalent of nearly $2,300 a year.

And there’s one more thing that needs to be understood — comparing income medians between Puerto Rico and the United States as a whole is a bit deceptive, because income inequality in Puerto Rico is much higher. The Gini Coefficient, a standard measure of the gap between the rich and the poor, is 0.469 across the US. In Puerto Rico, it’s 0.532, a number higher than any American state.

So yes, tuition and fees at UPR are pretty low right now by national standards. But what’s being planned would change that dramatically, and would do so abruptly and in the middle of a very tough financial climate.

Update | Victor Sanchez of the United States Student Association tweeted the following response to this piece: “Tuition is low, comparable to what? Other public institutions? Ha! #sameoldassargument #privatization.” Victor makes an excellent point, and it’s one worth expanding to more than 140 characters.

By definition, about half of all universities are going to have tuition lower than the national average at any given time — that’s how averages work. If every institution with below-average tuition raises their prices to the national average, the national average will go up. And suddenly all the institutions that had already had national-average tuition will be below average, and have a new justification for raising their tuition. A chase to the national average will produce an unending rapid upward spiral in college costs.

And of course it’s not just institutions with below-average tuition who are raising their rates. The University of California, long one of the nation’s more expensive public universities, has been raising rates through the roof recently. And with each California tuition hike, the national average — and thus the benchmark for what’s “reasonable” — rises accordingly.

If tuition costs are going to be kept to any sort of limits, some of the institutions with below-average tuition costs are going to have to stay below average. That’s not politics. It’s just math.