Source: Bloomberg City Lab

Date Published: 02.26.2026

Link: The Rise of the Manhattan Mega-Mansion

While fights over housing creation take up the public sphere in New York, the city has quietly been losing thousands of units. Bloomberg’s review of tax records shows that since 2004 at least 9,300 units have been lost to conversions to single building rollups, most frequently by building the entire building and making it a single family home. While this number of units represent a small portion of the 2.4 million rental units in the city. The conversions are heavily concentrated in lower-rise historic designated high amenity neighborhoods such as the West Village. The 2-8 unit buildings that are the frequent target of these conversions are often the affordable rent stabilized apartments in these higher income neighborhoods as well. The West Village, Upper West Side, Upper East Side, and Greenwich all have fewer units of housing than 20 years ago. The growth of these large single family homes often valued in the tens of millions reduces the property tax revenue to the city due to the way that NYC taxes single family and multifamily properties. For example, a former 16 unit building on the Upper West Side that had a $50,000 property tax bill in 2017 that was reduced to $12,000 once it was converted to a single family home. The city currently has no mechanism to discourage this, so the rate of these conversions is accelerating with the increase in the ultra-wealthy. Chicago has shown limited success with demolition taxes in a specific area, but San Francisco has had better success with requiring their planning department to sign off on all projects that eliminate housing units.