According to Northeastern University economist Barry Bluestone, author of the foundation report, incomes have remained stagnant for homeowners, and fallen for renters. So even if prices stayed flat, housing affordability would be eroding. But prices for homes, condominiums, and apartments have been climbing, gradually in some neighborhoods, precipitously in others.

The end result has been a city with rapidly growing populations of both rich and poor residents, while middle-class families are vanishing.