In Homelessness Is a Housing Problem, Gregg Colburn, assistant professor of real estate at the University of Washington, and data scientist Clayton Page Aldern test a range of conventional beliefs about what drives the prevalence of homelessness in a given city— including mental illness, drug use, poverty, weather, and public assistance—and find that none explain why, for example, rates are so much higher in Seattle than in Chicago. Instead, they discover that housing market conditions, such as the cost and availability of housing, offer a more convincing explanation. With an introduction by Maria Metzler, executive director of Helpline House.