Why do some US cities struggle more with homelessness? A new book explores a key component of the issue: housing supply.

The problem of homelessness has steadily worsened across the United States in recent decades, but some cities and metro regions have fared far worse than others.

A new book by University of Washington professor Gregg Colburn and Seattle-based data scientist and policy analyst Clayton Page Aldern examines these places’ disparate trends and the many causes that have been ascribed to homelessness. One by one, and with compelling data, Colburn and Aldern dismantle the common storylines that have blamed homelessness on individuals or cities’ social policies. Their research finds that the cause actually lies in these places’ very different housing markets.

Sightline interviewed the authors about their findings. Their book, Homelessness Is a Housing Problem: How Structural Factors Explain U.S. Patterns, is available from University of California Press.

HOW DID THIS RESEARCH START FOR YOU?

It began with the observation that much of the conversation around homelessness in our region, and across the country, lacks focus. Various explanations—individual, structural, and political—have dominated this conversation. There’s a perception that homelessness is a product of certain types of people who tend to gravitate toward certain types of cities. If you live on the West Coast, for example, you know the cities we’re talking about. Seattle, Portland, San Francisco, Los Angeles: all these cities have high per capita rates of homelessness.

But there’s actually significant variation in rates of homelessness around the country. Data shows that according to the 2019 point-in-time (PIT) count (the annual census of homelessness around the country), in King County, about 5 in every 1,000 people experience homelessness on a given night. In sunny Miami-Dade County in Florida, that number is closer to 1 per 1,000. What accounts for the difference? Specifically, what explains the variation in homelessness rates around the country? Our research seeks to answer those questions by zooming the lens out from the individual experiencing homelessness to the city in which they live.

WHAT FACTORS DO PEOPLE TYPICALLY THINK DRIVE HOMELESSNESS? AND WHAT DID YOU LEARN ABOUT THESE FACTORS?

If you watch the local news or spend time on Nextdoor, you have a sense of what these factors are. For many observers, homelessness is a function of mental illness, drug use, and overly generous social policies. These explanations are often supported by anecdotes, and certainly academic research confirms that a range of individual vulnerabilities, including poverty, substance abuse, and mental illness, increase one’s risk of homelessness. We both live in the Puget Sound region, and we know what it’s like to walk around downtown Seattle, where you encounter a lot of people who are probably sleeping outside and who might also be living with a serious mental illness or a substance use disorder. It’s not a huge analytical leap for people with housing to connect these individual conditions to Seattle’s homelessness problem.

But there are a couple of issues with this conclusion. First, the people sleeping on the street only represent a subset of the total population of people experiencing homelessness. In the 2020 count, chronic homelessness (what policy makers call being homeless for at least a year and living with some kind of physical or mental disability, including mental illness, a chronic health condition, and substance use disorder) accounted for less than 30 percent of the homeless cases in King County, while the chronic unsheltered population made up less than 17 percent of total cases. Second, we know that mental health and drug use can be both a cause of homelessness and a consequence. The trauma associated with homelessness is significant; that drug use and mental illness might result from this experience is not surprising. Research confirms this relation...