The burgeoning assisted-living industry has generated much concern among mental health professionals, residents, and caregivers about the lack of appropriate individualized care for the very heterogeneous aging population living in assisted living facilities, as well as the lack of research, standards, and oversight associated with such care. Data on the total number of assisted living facilities are apparently difficult to obtain, but in the introduction to Assisted Living: Sobering Realities, the number is said to range from 30,000 to 40,000; one of the articles in the book lists the total as 11,459. The overall number of residents in assisted living facilities is not known, increases each year, and depends on the definition used.