While the city realized by the 1980s that SRO units needed to be preserved, due to their role in housing homeless people, and introduced policies to encourage SRO retention, the number of SRO units had fallen by one half (from its Depression-era highest number). In 1985, the city tried to stop the loss of the remaining SRO units by banning the "conversion, alteration, or demolition" of SRO buildings, but by 1989, this law was struck down by an appeals court. The huge loss of SRO units in New York City is "not the inevitable result" of "market forces"; it was caused by an interaction between city housing policies and market forces.