At the start of the 1970s, homeowners—often in single-earner families—generally spent two-and-a-half years’ worth of their income when they bought a house. That number began to rise and rise. By 2010, it had nearly doubled. Buying a house now took almost four-and-a-half years of a family’s earnings. People could sense the deteriorating relative position of the working class even before it showed up in the statistics.

