Here's another link about homeless demographics. I've seen a couple of generalizations in this thread about homeless populations that are biased or outright wrong.
Highlights:
Two trends are largely responsible for the rise in homelessness over the past 20-25 years: a growing shortage of affordable rental housing and a simultaneous increase in poverty.
In 2001, the U.S. Conference of Mayors' survey of homelessness in 27 cities found that children under the age of 18 accounted for 25.3% of the urban homeless population (U.S. Conference of Mayors, 2001). This same study found that unaccompanied minors comprised 4% of the urban homeless population. However, in other cities and especially in rural areas, the numbers of children experiencing homelessness are much higher. On a national level, approximately 39% of the homeless population are children (Urban Institute 2000). A 1987 Urban Institute study found that 51% of the homeless population were between the ages of 31 and 50 (Burt, 1989); other studies have found percentages of homeless persons aged 55 to 60 ranging from 2.5% to 19.4% (Institute of Medicine, 1988).
Approximately 23% of the single adult homeless population suffers from some form of severe and persistent mental illness (U.S. Conference of Mayors, 2003). According to the Federal Task Force on Homelessness and Severe Mental Illness, only 5-7% of homeless persons with mental illness require institutionalization; most can live in the community with the appropriate supportive housing options (Federal Task Force on Homelessness and Severe Mental Illness, 1992).
Surveys of homeless populations conducted during the 1980s found consistently high rates of addiction, particularly among single men; however, recent research has called the results of those studies into question (Koegel et al., 1996). Briefly put, the studies that produced high prevalence rates greatly over represented long-term shelter users and single men, and used lifetime rather than current measures of addiction. While there is no generally accepted "magic number" with respect to the prevalence of addiction disorders among homeless adults, the U.S. Conference of Mayors' number was 30%, and the frequently cited figure of about 65% is probably at least double the real rate for current addiction disorders among all single adults who are homeless in a year.
The number of homeless families with children has increased significantly over the past decade; families with children are among the fastest growing segments of the homeless population. In its 2003 survey of 25 American cities, the U.S. Conference of Mayors found that families comprised 40% of the homeless population, a definite increase from previous years (U.S. Conference of Mayors, 2003). On a national level, the numbers are higher: the Urban Institute found that approximately 39% of the homeless population are children (Urban Institute 2000). These proportions are likely to be higher in rural areas; research indicates that families, single mothers, and children make up the largest group of people who are homeless in rural areas (Vissing, 1996).
As the number of families experiencing homelessness rises and the number of affordable housing units shrinks, families are subject to much longer stays in the shelter system. For instance, in the mid-1990s in New York, families stayed in a shelter an average of five months before moving on to permanent housing. Today, the average stay is nearly a year (Santos, 2002).
Battered women who live in poverty are often forced to choose between abusive relationships and homelessness. In a study of 777 homeless parents (the majority of whom were mothers) in ten U.S. cities, 22% said they had left their last place of residence because of domestic violence (Homes for the Homeless, 1998). In additions, 34% of cities surveyed by the U.S. Conference of Mayors identified domestic violence as a primary cause of homelessness (U.S. Conference of Mayors, 1998). Studying the entire country, though, reveals that the problem is even more serious. Nationally, approximately half of all women and children experiencing homelessness are fleeing domestic violence (Zorza, 1991; National Coalition Against Domestic Violence, 2001).