Homelessness is defined as lacking stable housing or living in shelters, warming centers, or other inadequate locations. The top three causes of family homelessness are lack of affordable housing, poverty, and unemployment, while the top three causes for single individuals are substance abuse, mental illness, and lack of affordable housing. An estimated 100 million people worldwide were homeless in 2005, including 40% of youth and 1 out of every 50 children in the US. Countries assist the homeless through services providing food, shelter, and clothing run by community groups and governments.