… is from page 116 of Thomas Sowell’s excellent 1984 book, Civil Rights: Rhetoric or Reality? (original emphasis; footnote deleted):
To say that some employers are mistaken in their criteria [of which workers to employ] is to say that other employers have special profit opportunities by hiring those workers passed over – and in a competitive market, that means that mistakes are likely to be corrected. It does not mean, however, that every difference in “representation” is a mistake, or that race, sex, or other group designations were used as criteria. Third-generation Mexican Americans earn 20 percent higher incomes than first-generation Mexican Americans of the same age, though it is doubtful if most employers seek the genealogical information necessary to make such a distinction.