In 1950 my wife’s uncle, the son of a West Side of Chicago ditch digger, won a scholarship to MIT. Back then it was unusual enough for anybody from Chicago to go all the way to Massachusetts for college that the local newspaper printed a picture of him boarding the train for Cambridge. By the 1960s, however, the spread of standardized testing had helped make it customary for elite universities to vacuum up larger and larger fractions of the country’s cognitive talent. The long-term implications of this momentous change are quantified in Charles Murray’s new book on the evolving American class system, Coming Apart.