Urban Institute ran the numbers on 15 years of rezoning in New York and Philadelphia. The verdict: when you let people build houses, they build houses. Groundbreaking stuff, truly.

The Briefcase Team | April 23, 2026

Urban Institute just released a 44-page research report that should settle one of the most expensive policy debates in American history. The study, funded by JPMorganChase and published April 15, 2026, examined 15 years of major zoning reforms in New York City and Philadelphia. It used propensity score matching and difference-in-differences regression, which is academic speak for "we did this carefully enough that you can't hand-wave it away."

The verdict: upzoning works. When cities let developers build more housing, developers build more housing. New York's seven neighborhood-scale upzonings produced 4,000 additional housing units within four years.

Philadelphia's 2012 citywide rewrite generated up to 4,000 additional unit permits per year compared to non-rezoned areas.

You will be shocked to learn that supply responds to supply constraints. Who could have foreseen this. Certainly not the City of San Francisco, which has been studying whether upzoning works since approximately the Johnson administration.

Anti-density advocates love the dodge "well, that's just one study." As of this week, that dodge is retired. We now have rigorous evidence from three of America's most-watched markets:

New York City. Seven rezoned neighborhoods produced 4,000+ net new units in four years. Gowanus, Brooklyn alone became a production machine - formerly industrial land transformed into market-rate plus low and moderate income housing. You let them build, they built.

Philadelphia. The 2012 citywide zoning rewrite generated up to 4,000 additional unit permits per year, concentrated in larger projects. Developers didn't file more applications. They filed bigger ones. Allow a 5-story building instead of a 3-story, and the same application yields more units. Groundbreaking stuff, if you've ever used a calculator.

Minneapolis. The 2018 Minneapolis 2040 plan - the first major U.S. city to eliminate single-family zoning - permitted 21,000 new units between 2017 and 2022, a 12% increase in housing stock versus just 4% for the rest of Minnesota. Rents in Minneapolis grew 1%. Rents in the rest of Minnesota grew 14%. Two-to-four-unit permits jumped 45% from 2020 to 2022.

Three cities. Three reforms. Same result. Bigger supply. Lower rent pressure. Fewer excuses.

The Urban Institute study does something most advocacy research refuses to do: it names the places where upzoning didn't work. The Jerome Avenue corridor in the Bronx was rezoned and produced no statistically significant supply increase. Parts of Philadelphia saw similar null results.

Why? Upzoning isn't magic. It's permission. It lets developers build where the market already wants to build. In neighborhoods with weak market demand, a zoning change doesn't conjure capital from thin air.

Anti-upzoning advocates argue rezoning will "destroy neighborhood character" and displace residents. The actual finding is the opposite. Upzoning produces housing where housing is economically viable. Where it isn't, nothing happens. Nobody's neighborhood gets "destroyed" in the Bronx because nothing gets built.

So the honest version of the critique is: upzoning works where the market is strong, which is exactly where housing pressure is worst, which is exactly where we most need it to work. That isn't a critique. That's a recommendation letter.

America built fewer housing units in the 2010s than in any other decade since World War II. Fewer than the 60s, 70s, 80s, 90s, or 2000s. We're now 10 million homes short. Prices rose 82% since 2000 while incomes rose 12%.

This didn't happen by accident. Boston's own zoning audit found less than 1% of residential buildings in the entire city comply with current zoning code. One percent. If Boston burned to the ground, 99% of its housing could not be legally rebuilt.

We've created a legal framework where the housing stock we already have is mostly non-compliant, held up only by grandfather clauses. That isn't land use regulation. That's a de facto moratorium on anything except single-family homes with yards, which is about as sustainable as using whale oil for streetlights.

The evidence has gone mainstream fast enough that state legislatures are stepping over cities. California's SB 79 overrides local density limits along transit corridors, forcing high-density development in Bay Area and Southern California counties whether city councils like it or not.

At the federal level, the 21st Century ROAD to Housing Act, backed by a growing bipartisan coalition, would tie federal housing funds to local zoning reform. Build or don't get the money. California YIMBY has proposed a similar approach using LIHTC eligibility as the carrot.

The fight is no longer between YIMBYs and homeowners at city council meetings. It's between state governments armed with academic evidence and the last remaining city councils still pretending single-family zoning is defensible.

We believe in property rights, market-driven solutions, and sensible policy. Upzoning is all three. It's not a subsidy. It's not a handout. It's not a government program. It is the government removing restrictions it imposed on property owners decades ago to benefit a specific class of existing homeowners at the expense of everyone else.

Single-family zoning isn't a neutral default. It's a subsidy to people who already own homes, paid for by everyone who doesn't. The Urban Institute study doesn't prove some radical new idea. It proves that when you reduce the subsidy, the market does what markets do.

What's newsworthy here isn't the finding. It's the defensive crouch that's been keeping this finding from translating into policy. For ten years, developers have said they could build more housing if allowed. For ten years, cities have studied whether that's true. For ten years, people have been locked out of homes because the studies weren't definitive enough.

They are now. We should probably act like it.

Urban Institute spent 15 years of data and a JPMorgan grant to confirm what developers, economists, and anyone paying rent in a major city already knew: when you let people build housing, they build housing. New York added 4,000 units from seven rezonings. Philadelphia added 4,000 unit permits per year from one citywide rewrite. Minneapolis added 21,000 units in five years and saw rents grow 1% while the rest of the state ran at 14%.

The places where upzoning didn't produce supply were places where the market was too weak to build anyway, which means the "upzoning will destroy neighborhoods" argument runs headlong into the finding that upzoning doesn't affect neighborhoods where nothing economically viable wants to be built. We are short 10 million houses.

We have the evidence. We have the tools. We have three major case studies with statistically significant results. The only thing still missing is the political will to admit that the zoning codes written in the 1970s were a mistake, and the longer we pretend they weren't, the more unaffordable America becomes. Upzoning works. Build the damn houses.