RWP 25-01, April 2025
Metropolitan areas are a fundamental unit of economic analysis. Broadly defined, they are unions of built-up locations near each other among which people travel between places of residence, employment, and consumption. Despite the importance of metropolitan areas, metropolitan Core-Based Statistical Areas and other official U.S. delineations considerably stray from this broad definition. We develop a simple algorithm to better match it, using commuting flows among U.S. census tracts in 2000. Three judgmental parameters govern the minimum strength of commuting ties between locations to include them in the same metropolitan area, the maximum separating distance between locations, and the minimum density of outlying settlement. A parameterization that balances encompassing commuting flows and excluding sparsely settled land delineates 361 Kernel-Based Metropolitan Areas (KBMAs), in aggregate capturing almost all the population and employment of metropolitan CBSAs in a small fraction of their land area. Additionally, we benchmark KBMAs against two alternative parameterizations, one that prioritizes encompassing commuting flows and one that prioritizes excluding sparsely settled land.
JEL classifications: R12, R14, R23
Kernel-Based Metropolitan Areas (KBMAs)
- Enumeration of 361 KBMAs
- Detailed Variables and Tables
- Illustrative maps
- Shape Files for mapping software
Kernel-Based Metropolitan Regions (KBMRs)
Kernel-Based Urban Areas (KBUAs)
Additional Materials
- Maps comparing KBMAs, KBMRs, and KBUAs
- Pairwise commuting flows between cores
- Iterative kernel joins
- Computer Code for Construction (coming soon)
Article Citation
Rappaport, Jordan, and McKenzie Humann. 2025. “A Better Delineation of U.S. Metropolitan Areas.” Federal Reserve Bank of Kansas City, Research Working Paper no. 25-01, April. Available at External Linkhttps://doi.org/10.18651/RWP2025-01