Political correctness has taken another hit in a new study that violates a taboo.

At the heart of the bonanza that market economies offer their constituents is productivity growth. Only competition in the marketplace can reliably produce innovations that produce more with less on a mass scale. Yet the rate of productivity growth in the United States has slowed dramatically in the last few years, increasing social and political tensions as people scramble for a piece of the pie in a near-zero-sum situation. Gain-sharing is much more pleasant than pain-sharing, after all.

I imagine that already the term "rrracist!" is being thrown at a new study that points to the increase in illegal immigration as one source of our productivity problems. Marketwatch reports this morning (hat tip: Ed Lasky):

All sorts of reasons have been trotted out to explain why U.S. productivity growth has slowed so markedly, from mismeasurement to stalling innovation to weak capital investment. Oxford Economics has a new research note adding another theory: unauthorized workers. They say that up to 15% of the 2 percentage point slowdown in productivity growth can be attributed to illegal immigration. By their numbers, which rely on data from the Labor Department and a survey from Pew Research, there are just over 11 million illegal immigrants in the U.S., of which 8 million are in the workforce, or 5% of the total U.S. workforce. They then adjusted the productivity growth numbers for a larger workforce.

There are all sorts of caveats necessary in evaluating the study, so it is at best tentative and suggestive. But to me, the important point is that a taboo has been broken.

At a common sense level, an influx of any demographic group characterized by very low average levels of formal education and skill training will take a toll on the productivity levels of a workforce on average more educated and skilled. And, of course, I must defensively add that there are numerous individual exceptions to the average, so we shouldn't "stereotype." But neither should we disregard data on averages, because they are mathematically useful.

On the other hand, speaking from a common sense level, many illegal immigrants are hardworking and make an effort to better themselves. But that approaches another taboo: comparing the work ethics of various demographic slices of the population. One reason why our social problems persist is that we can't talk honestly about them.

And whom does that benefit, by the way? Not Republicans.

Make no mistake: political correctness is a tool of social and political control.