"Concentrations of older people living in settings not planned or designed for this age cohort are increasingly often referred to as "naturally occurring retirement communities" (NORCs). Settings characterized as NORCs have a variety of demographic origins and physical characteristics. Physically, NORCs can be apartment and condominium complexes, or neighborhoods and older parts of a town. NORCs can even be rural areas or small towns. The demographic origins of NORCs are varied as well and may be described as 1) aged-left-behind, 2) aging-in-place, and 3) in-migration."