It is a commonplace to the point of boringness among advocates of free markets that they make people pay to discriminate based on their tastes. A factory owner who restricts employment to whites only will face a narrower talent pool—likely paying higher wages for lower skills in total or on average. [...]
Employers cannot observe an employee’s productivity directly, at least before they employ them. But they can observe some things about them that signal productivity—using statistics. For example, if on average south Asians or Polish migrants tend to work harder than white Brits, they can use this fact about them to help make their employment decision. This isn’t racist—they don’t prefer employing south Asians, and they would be equally happy to pay a white Brit £6.50 an hour to produce £7 of stuff—it’s just that on average south Asians produce £7 of stuff an hour (say), whereas white Brits produce £6.40.
Which one is actually in place? We can test this. The answer is a resounding ‘statistical discrimination’. For example, minorities in France did worse when a large randomised study made them anonymous in job applications—so firms couldn’t see their names and thus ethnicities—implying that the reason they were called back and employed less was because their resumes/CVs were less attractive.
In Germany, job applicants with Turkish-sounding names got less callbacks than those with German-sounding names—unless both applicants had a favourable employment history reference. Then, for a given quality of reference, employers didn’t care whether they were Turkish or German. On eBay, white sellers receive lower prices selling stereotypically black products and black sellers receive lower prices selling stereotypically white products, but these differences go away when sellers build up credible reputations.