Politicians on both sides of the housing debate tend to focus on demand: make mortgages cheaper, give first-time buyers subsidies, cap rents. These measures are not useless, but they treat the symptom. The disease is supply.

The United States has underbuilt housing for roughly fifteen consecutive years following the 2008 crash. Developers pulled back sharply after the crisis, zoning laws made new construction slow and expensive, and NIMBY opposition to density in high-demand urban areas ensured that the places where people most wanted to live added the fewest units. The cumulative shortfall is estimated at somewhere between four and seven million homes, depending on the model.