The author wishes to thank the planners of the Symposium, Paul Koegel, Roseanne Haggerty, Fred Karnas, and William Breakey for their review of an earlier draft of this paper and Nancy McKenzie for her assistance editing later versions.
 In comments on this paper at the Symposium offered by William Breakey (2007), he suggested eight social developments have influenced the evolution and operation of a homeless system of services. Several of these factors are mentioned elsewhere in this paper and in other papers in the Symposium, but the list is valuable in summarizing them:
- increasing poverty
- an institutionalized response to homelessness
- the absence of an effective affordable housing policy
- the lack of a coherent health care system
- the movement from institutionally-based to community-based care
- increased influence by private philanthropy
- the successes of advocacy
- changes in the roles and rights of women
 Several of these communities are participating in the Chronic Homelessness Initiative, where a rigorous data collection requirement gives credence to these reductions. Since other cities not receiving Initiative funding also report reductions, specialized funding alone does not account for these changes.
 The chronic homeless label was first articulated by the Institute of Medicine (1988).
 NREPP also lists a second intervention, the Trauma Recovery and Empowerment Model, as an evidence-based service applicable to homelessness.
 These are approximations derived from estimated expenditures on medical care to homeless veterans as well as targeted homeless appropriations.
 Renters with incomes below a level that varies geographically but, on average, about the same as the federal definition of poverty.
 Varying definitions of homelessness are significant. During April/May 2007, the author participated in more than 30 interviews concerning homelessness in three of the U.S. Pacific Territories. Extended family continues to be the first line of defense on these islands. When a member experiences a significant setback such as chronic illness, housing loss, job loss, etc., families readily take that person/household into another household. Consequently, when applying the HUD definition of homelessness, the circumstance is rare to nonexistent since homeless persons are being sheltered by family members. Service providers are aware of the impacts of such accommodations on families and are eager to have homelessness acknowledged as the islands experience it. They identify fairly large numbers of family members as homeless, not just at risk of homelessness. But when constrained by the mainland/legislative definition, these persons cannot be counted and point-in-time data portray little prevalence of homelessness.
 The prevalence data are estimates based on different years, although all during the 1990s. The public housing/household data are from 2000 and later.