Abstract:
In 2024, an estimated 770,000 people experienced homelessness on any given night in America. Without intervention, that number is projected to exceed one million within the next decade. Of those, 270,000 were living rough, with nearly 150,000 unsheltered individuals residing in Oregon, Washington, and California alone. In King County, WA (Seattle Metro), an estimated 9,000 people were living without shelter on any given night.
Traditionally, unsheltered Point-in-Time (PIT) counts rely on volunteers conducting a single-night, in-person headcount of individuals experiencing homelessness. This resource-intensive method is widely recognized as an undercount and fails to capture essential qualitative data about the experiences and needs of people living unsheltered.
Since 2022, the King County Regional Homelessness Authority (KCRHA) and the University of Washington have partnered to conduct unsheltered PIT counts using Respondent Driven Sampling (RDS), a network-based peer referral recruitment method. RDS is a sampling strategy designed to estimate the size and characteristics of hard-to-reach populations that lack an administrative sampling frame, and was used to guide respondent selection for both qualitative and quantitative surveys.
In this seminar, I will present findings from four rounds of RDS surveys estimating the size of the unsheltered population in King County, WA, from 2022–2026, as well as a 2026 study of the youth population in Los Angeles County.
Much of this work has been published in: Almquist, Z. W., et al. (2025). Innovating a community-driven enumeration and needs assessment of people experiencing homelessness: A network sampling approach for the HUD-mandated point-in-time count. American Journal of Epidemiology, 194(6), 1524-1533.
Zack W. Almquist is an Associate Professor of Sociology, an Adjunct Associate Professor of Statistics, and a Senior Data Science Fellow at the eScience Institute at the University of Washington. His research develops and applies innovative statistical, survey, and social network methodologies to address critical social issues, including housing and homelessness, population health, and environmental governance, with a particular focus on improving data collection for marginalized and hard-to-reach populations. Prior to joining UW, he held faculty positions at the University of Minnesota and worked as a Research Scientist at Facebook. Prof. Almquist has received numerous honors, including the NSF CAREER Award, the ARO Young Investigator Award, and two major awards from the American Sociological Association. He serves as Editor-in-Chief of the Journal of Mathematical Sociology and in elected chair of the Section on Mathematical Sociology for the American Sociological Association and Chair of the Caucus on Homelessness for the American Public Health Association.
