["Economic Inquiry, EarlyView. ", "\nAbstract\nZoning reform is increasingly advocated to redress unaffordable housing, but few real‐world examples demonstrate its efficacy. However, Auckland recently upzoned approximately three‐quarters of its residential land, precipitating a housing construction boom. We investigate whether the reform reduced housing costs, adopting a synthetic control method to estimate rental prices in Auckland under the counterfactual of no zoning change. Eight years after the reform, the synthetic control under our preferred empirical specification implies that rents decreased by 23% due to the reform. These findings are robust across a range of specifications and support the proposition that widespread upzoning can enhance housing affordability.\n"]