Rent-controlled apartments are often thought of as the “white whale” of New York City real estate. People rarely leave their rent-controlled homes and landlords use loopholes to obscure them from the public, making it increasingly difficult to snag one.

John Krauss, a self-proclaimed hacker and mapper, recently created a tool that maps the changes that have occurred in rent-controlled apartments since 2007. The public can now see the amount as a percentage that a building has either increased or decreased in stabilized units over seven years in one handy map.

The interactive map reveals that rent-controlled apartments have been on the decline — though some new construction has added to the amount of rent-controlled apartments in the city.

Krauss describes New York State Homes and Community Renewal, the agency in charge of rent stabilization, as veiled in secrecy.

“The only information they’ll release is a list of buildings that have apartments in the program. The list doesn’t indicate whether every apartment in a building is stabilized, or if only some are. Buildings that are 100% stabilized look the same on this list as buildings with just one apartment left in the program,” he said.

He discovered a new way to find the data: property tax bills. He collected every tax bill from 2008 to 2014 for every potentially stabilized building in NYC by downloading thousands of PDF files over a period of several months. Doing the work himself ended up saving him $50,000 in fees from the Department of Finance.

Using that data, he created the map, which shows where stabilized apartments have disappeared, remained or been constructed between 2007 and 2014.

Users of the map can identify buildings that are just beginning to decline in stabilized apartments as well as buildings with unregistered landlords. Krauss hopes to break down losses and gains by political districts so that elected officials can better understand the loopholes that are affecting the rental market.

Raw data is available at

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