Restrictive zoning laws are the single largest regulatory barrier to housing affordability in the United States. Single-family zoning, minimum lot sizes, height restrictions, parking mandates, and lengthy permitting processes prevent the construction of new housing where demand is highest. Research from Harvard, Wharton, and the National Bureau of Economic Research shows that these regulations can inflate home prices by 20-50% in heavily regulated markets. Our analysis covers zoning reform efforts, the YIMBY movement, density bonuses, and the economics of housing supply — grounded in free-market principles.