One-fifth of homes in Pittsburgh are considered empty nests, defined as households headed by people 55 or older with no children of any age living with them.
Zillow Porchlight reports that empty nests are on the rise, jumping from a 11.9 percent share of all households in 2005 to 15.5 percent in 2015.
Other cities, such as Buffalo, Cleveland, Richmond, Va., and Birmingham, Ala., also have significant shares of empty nest households.
The places with the lowest densities of empty nests include booming cities with strong job markets, such as Austin, Phoenix, and San Francisco. Retirement communities, such as Fort Myers, Tampa, and Orlando — all in Florida — also registered low on the list.