Book excerpt: Using rich and detailed data, this groundbreaking book explains why homelessness has become a crisis in America and reveals the structural conditions that underlie it. In Homelessness Is a Housing Problem, Gregg Colburn and Clayton Page Aldern seek to explain the substantial regional variation in rates of homelessness in cities across the United States. In a departure from many analytical approaches, Colburn and Aldern shift their focus from the individual experiencing homelessness to the metropolitan area. Using accessible statistical analysis, they test a range of conventional beliefs about what drives the prevalence of homelessness in a given city—including mental illness, drug use, poverty, weather, generosity of public assistance, and low-income mobility—and find that none explain the regional variation observed across the country. Instead, housing market conditions, such as the cost and availability of rental housing, offer a far more convincing account. With rigor and clarity, Homelessness Is a Housing Problem explores U.S. cities' diverse experiences with housing precarity and offers policy solutions for unique regional contexts.