This marks the lowest level since the fourth quarter of 2011, according to the Real Estate Board of New York (REBNY), the state’s first real estate trade association founded in 1896. In the first three months of 2020, the number of residential sales-including condominiums, cooperatives and one-to-three-family buildings-dropped 16% citywide year-over-year, from 10,382 to 8,702 sales. New York City’s real estate market slowed down significantly in the first quarter, even before the coronavirus fallout, said a leading trade association on Wednesday.