New York and Philly Tried a Wild Idea to Build Housing. It Worked.

Turns out, if you want more housing, you just have to… let people build more housing. Who knew?

Two of the U.S.'s biggest cities, New York and Philadelphia, have been quietly experimenting with a concept called "upzoning." That's a fancy way of saying they tweaked their zoning laws to allow for denser, taller, and generally more housing in certain neighborhoods. And a new study from the Urban Institute suggests it's actually working.

In New York, where upzoning was often targeted to specific neighborhoods, the changes led to roughly 4,000 extra housing units within four years, compared to areas where the rules stayed the same. Philadelphia, meanwhile, saw about 4,000 additional housing permits each year in its upzoned zones.

Now, Philly's citywide zoning overhaul in 2012 took a bit longer to show its muscle, with a significant jump in permits not really kicking in until 2018. The study notes a looming expiration of a 10-year tax abatement for new construction likely added some extra oomph to that building spree. Because nothing says "build now" quite like a looming tax bill.

New York's results came faster, partly because its upzoning efforts were often tied to other programs, like its Mandatory Inclusionary Housing initiative. Which, if you think about it, is both impressive and slightly terrifying for anyone who remembers how long it usually takes to get anything built in NYC.

Of course, not every upzoned block suddenly sprouted condos like mushrooms after a rain. The study points out that areas that didn't see a boost often had weaker housing markets to begin with. Turns out, even with permission, developers aren't keen on building where no one wants to live. Zoning reform, the experts say, works best when it's part of a bigger picture that includes making housing affordable and preventing existing residents from being priced out. Because building more homes is great, but making sure they’re for everyone? That’s the trick.