Estimating local daytime population density from census and payroll data

Daytime population density reflects where people commute and spend their waking hours. It carries significant weight as urban planners and engineers site transportation infrastructure and utilities, plan for disaster recovery, and assess urban vitality. Various methods with various drawbacks exist to estimate daytime population density across a metropolitan area, such as using census data, travel diaries, GPS traces, or publicly available payroll data. This study estimates the San Francisco Bay Area's tract-level daytime population density from US Census and LEND LODES data. Estimated daytime densities are substantially more concentrated than corresponding night-time population densities, reflecting regional land use patterns. We conclude with a discussion of biases, limitations, and implications of this methodology.