But how good was that work? What went into David Card's model? Over the past year, the economic profession has witnessed a series of autopsies and counter-autopsies upon Card’s data, sparking a debate that has rapidly grown both intensely ideological and vituperatively personal.

In October 2015, Harvard’s George Borjas—academia’s leading immigration skeptic—returned to the original data sets that supported David Card’s famous paper. Borjas insisted that Card had chosen his comparisons wrong. Borjas redid the 1990 paper’s math and hurled a defiant criticism:

In fact, the absolute wage of high school dropouts in Miami dropped dramatically, as did the wage of high school dropouts relative to that of either high school graduates or college graduates. The drop in the low-skill wage between 1979 and 1985 was substantial, perhaps as much as 30 percent. … At least in the short run, the labor market responded precisely in the way that the “textbook” model predicts: an increase in the number of potential workers lowered the wage of those workers who faced the most competition from the new immigrants.

Here’s where things get testy. David Card’s 1990 paper has been unusually influential, cited again and again as a “classic” of immigration economics. It exerts its influence in large part because it purports to be based on close study of real-world effects, not blackboard computations. As Princeton’s Alan Kreuger—formerly the chair of President Obama’s Council of Economic Advisers—wrote in 2006: "Studies that claim to find a deleterious effect of immigration on natives’ wages are typically based on theoretical predictions, not actual experience.” Card, by apparent contrast, had exited the ivory tower to discover facts in the marketplace. And now a critic dared claim that Card had got his math wrong? Impossible. Intolerable.

In short order, a rebuttal to Borjas’ criticism of Card was published by Giovanni Peri and a University of California graduate student, Vasil Yasenov.

Their answer in their winter 2015 paper was scorching:

We point out that the very different conclusions in a recent reappraisal by George Borjas (2015) stem from the use of a small sub-sample of high school dropouts in the already very small March-CPS sample. That sample is subject to substantial measurement error and no other sample provides the same findings. Being imprecise about the timing of the data and the choice and validation of the control sample further contribute to the impression of an effect from the boatlift in Borjas.

In a December 18 op-ed at Bloomberg View, the columnist Noah Smith cited the Peri-Yasenov paper to pour even more scorn on Borjas’s work and reputation.

Not only was Borjas’s sample too small, but—contended Smith—it was downright manipulated.

Even more damning, Peri and Yasenov find that Borjas only got the result that he did by choosing a very narrow, specific set of Miami workers. Borjas ignores young workers and non-Cuban Hispanics -- two groups of workers who should have been among the most affected by competition from the Mariel immigrants. When these workers are added back in, the negative impact that Borjas finds disappears.

Smith’s column concluded by attempting to excommunicate Borjas from all future participation in immigration debates.

All of this leaves Borjas’ result looking very fishy. He would have had to have searched hard to find the one small group of workers who seemed to suffer from the Mariel influx. Borjas could well have been subject to heavy confirmation bias—he might have been so fundamentally certain that immigration was bad for native workers that he searched and searched until he found one group that seemed to confirm his pre-existing beliefs. In science terms, that is called data mining; it's a big no-no. In debates about immigration, the anti-immigrant side inevitably cites Borjas. He has gained fame and notoriety for being the most prestigious economist who thinks that immigration is a disaster for native workers. All of Borjas’ papers seem to arrive at this same conclusion. Participants in immigration debates really should stop citing Borjas’ research so much.

As one of those who cites Borjas’s work often, I suppose I was supposed to share the burn of this hot take. Soon after it appeared, I called Borjas for comment. He had just finished a reply, he said, and it would be a doozy. And so it is.