NEW YORK CITY—Landmarking hasn't offered the level of protection for rent-stabilized apartments that advocates have touted, says the Real Estate Board of New York. Over the past seven years, the decline in the number of rent-regulated apartments within New York City's historic districts was four times higher compared to non-landmarked areas of the city.

Citywide, the loss between 2007 and 2014 was 22.5% of rent-regulated apartments in landmarked districts compared to 5.1% at non-landmarked properties. The REBNY report calls the losses “particularly startling” in Manhattan and Brooklyn: 24.5% of landmarked units in Manhattan compared to 11.5% of non-landmarked units, and a 27.1% decline in landmarked Brooklyn units compared to 3.4% at non-landmarked properties in the borough.

The historic districts with the highest net loss of rent-stabilized units were Greenwich Village, which lost 1,432 units, and Upper West Side/Central Park West (-2,730 units). Combined, these two historic districts had 30% fewer rent-stabilized units at the end of the '07-'to'14 timeframe.

New construction and conversions haven't replenished the supply in landmarked districts, according to REBNY. The study found that between 2003 and 2012, only five new units of affordable housing were built in Manhattan landmark districts, which comprise nearly 30% of the borough, and only 100 citywide. This production accounted for 0.29% of all new affordable housing units during that 10-year period.

“Affordable housing remains one of our city's most pressing needs, and these numbers do not show any evidence that landmarking helps to preserve it,' says REBNY president John Banks. “This report refutes the notion that historic districts are a good means of preserving existing affordable housing.”