The following information  is provided by the City of Seattle’s Human Services Department.

On any given night in Seattle, an estimated 800 young people ages 12-24 are without a safe place to sleep. For all of King County, the number of homeless youth nightly may be as high as 2,000. Hundreds of our children, adolescents, and young adults are on the streets, at high risk of becoming seriously injured or chronically ill, involved in criminal activity and/or incarcerated, and dependent on welfare systems.

Youth who become homeless come from all socio-economic and ethnic backgrounds. In King County, they are mostly ages 15 to 21. 

More than half who use existing countywide services are white. However, experts believe those estimates do not account for the number of homeless youth of color who may not have access to culturally appropriate programs.

Homeless youth are male and female. Some are parents. Most come from homes within the county. Many are dealing with the effects of childhood trauma, substance abuse and the stress of street life, all of which can delay healthy adolescent development.

The greatest economic and social costs in not addressing the homeless youth population are long-term. Once youth begin to see homelessness as a way of life, they virtually "drop out" of society. The hope of getting an education is lost. The potential increases for incarceration, emergency hospital and long-term care, and welfare assistance. Early intervention approaches are clearly an investment worth the cost.

Homelessness among youth creates a variety of challenges. Many youth on the streets have experienced great trauma in their young lives. But our experience suggests that even young people who have watched their lives and dreams crumble, can chart a course toward a healthy, productive lifetime with the right combination of services and support.

(Reference - http://www.seattle.gov/humanservices/fys/homelessyouth/default.htm)