New York’s housing shortage is causing an affordability crisis, and a practice of developers building fewer units than sites allow is only set to make the problem worse.

Zoning regulations and community reticence to density is often held up as a major reason why little headway is being made to push up supply. But a trend toward larger new buildings — but with few apartments — is also playing a part, The New York Times reports. The publication found multiple instances of new residential buildings with fewer units than they replaced, even where far more could be built as-of right.

“In a city that’s desperate for housing, all kinds of housing, how can you allow a builder to build fewer units?” said Gale Brewer, a former Manhattan borough president and current city council member for the district that includes the Upper West Side. “The idea that these people can get away without building anything affordable is mind-boggling to me.”

Urban planners told the Times development sites in high-density areas of the city are few and far between, and precious opportunities to build more housing is being lost. For example, Naftali Group’s Upper East Side tower called The Benson was finished last year and offered 15 units priced between almost $13M up to $35M — all of which have found buyers. The site used to have prewar buildings, and it was zoned to allow as many as 83 apartments, per the Times.

Similarly, at 15 West 96th St., the developer is putting up a 21-unit condo building at a site that would allow for 66 units. At 1165 Madison Ave., there is a new 13-story building with just 11 units. The site could have had 88 units — but instead one apartment alone spans 13K SF, four stories and traded for $65M.

As a result, in the decade leading up to 2020, the Upper East Side lost more units than any other neighborhood, largely because of this practice, per the Department of City Planning.

“It’s a very simple answer: It’s the market demand,” Naftali founder Miki Naftali told the Times.

As well as the Benson, the company is attempting to build a planned 210-foot tower with 45 apartments on West 84th Street. Even though the building is three times the height of the current property, if Naftali goes ahead with condominium, a net of 83 homes will be lost.

Rents in the city have reached record highs this year, with Manhattan reaching an average of $5,113 per month in July, an all-time high, and rents have similarly broken records in Brooklyn and Queens.

In August, Manhattan’s median rent and median net effective rent were the second-highest on record, which ended a stretch of six straight months of record rents. At the same time, the number of affordable housing units produced in the last year has plummeted.

The Department of Housing Preservation and Development financed the creation and preservation of 16,042 units in the fiscal year beginning July 1, 2021, Crain’s New York Business reports. That marks a 45% drop from the previous year, according to the mayor’s Management Report.