The vacancy rates in New York City’s public housing have fallen to an extraordinarily low rate—0.6 percent. As as of December 2017, just 1,050 units are available, and 25,000 families are lined up waiting for a spot to open up.

But it’s not simply that there aren’t enough empty rooms. Nearly a third of all New York City Housing Authority apartments are under-occupied, according to a new report from the city’s Independent Budget Office. Of the 176,066 public housing units NYCHA rents out, 57,155 w…