My goal in sharing this is not to wholy convince anyone of Caplan's views. I'm not persuaded by all of them myself. But moreover, I understand how difficult it is to change minds on something so resistant to experimentation and clearly persuasive data. We're mainly left with theorizing. Caplan's list, to me, is a list of underrated explanations for things we observe.
For instance, workers' standards of living. The conventional wisdom, that but for government regulation workers would still be dying in mines or there would be child labor, is one theory. And it's true to some (immeasurable) extent. But that would mean we could wipe out poverty by installing American workplace regulations the world over. That doesn't seem like it would solve the problem. Most labor economists would say that government regulation lags the real cause of rising workplace and living standards: "economic growth, which in turn is driven by technological progress, a market system, and a culture of entrepreneurship. As the economy grows, the demand for labor grows, and workers achieve better wages and working conditions." Greg Mankiw goes on:
Economic studies of unions, for example, find that unionized workers earn about 10 to 20 percent more by virtue of collective bargaining. By contrast, real wages and income per person over the past century have increased several hundred percent, thanks to advances in productivity.
In response to Caplan's assertion that "large group differences persist because groups differ largely in productivity" you charge Caplan as ignorant of history and probably racist. I don't think he's either, but I'd ask you: Why do large group differences exist? That's a sincere, genuine ask. I think the conventional story--institutional and individual sexism and racism--is a theory that explains the state of things to some (immeasurable) extent. But Caplan alludes to another theory: groups have different preferences, affinities, and abilities, largely the result of cosmic forces no one is responsible for. Some of them are uncontroversial, like that women, not men, give birth to children because they have the reproductive organs. Or that men are more often in prison, or on death row, because they are more aggressive and prone to violence than women. More controversial: NYC Mayor Bill de Blasio recently announced plans to eliminate the test that apportions seats to the NYC elite high schools and replace with a system that would offer spots to the top students at every middle school in the city. The reason being that the composition of the elite schools does not mirror or even approximate the racial proportions of New York City's population. For instance, the city's public school are 70% African-American, while the most recent admitted class at Stuyvesant, the flagship of the elite high schools, admitted something like only 10 African-American students. That's a racial injustice, which ought to be remedied. However, Asian-Americans, who comprise 16% of students enrolled in city schools, are 62% of the students enrolled at the elite high schools.
The composition of New York City's public schools and its elite high schools would seem to foreclose the argument that institutional racism is responsible, since Asian-Americans, the object of animus and racism for much of American history, are so "overrepresented." If invidious discrimination does not explain every disparity, what does? An underrated source of explanation are that there are differences in preferences or inclinations between groups. I'm hesitant to say exactly what they are because I would only be speculating, and it's controversial enough a point already. However, because something is controversial--radioactive, even--therefore it is untrue in principle? I doubt it.
I don't follow Caplan's point on mating markets to speak knowledgeably about it. But, again, if the state of the world is not monocausal, then a full accounting would entail lots of theories and explanations, no matter the derision they're met with because of social taboos or political correctness.