External LinkLink to published version in the Journal of Urban Economics.
RWP 25-01, April 2025; updated May 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 threshold strength of commuting ties between locations to include them in the same metropolitan area, the maximum separating distance between locations, and the threshold 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. We benchmark KBMAs against two alternative parameterizations, one that prioritizes encompassing commuting flows and one that prioritizes excluding less built-up and less near locations.
JEL classifications: R12, R14, R23
Kernel-Based Metropolitan Areas (KBMAs)
Our preferred parameterization, likely to be appropriate for most questions and purposes. KBMAs balance encompassing commuting flows with excluding locations that are farther away or less densely settled.
- Enumeration of 361 KBMAs
- Detailed Variables and Tables
- Illustrative maps
- Shape Files for mapping software
Kernel-Based Metropolitan Regions (KBMRs)
An alternative benchmark that emphasizes encompassing commuting flows, KBMRs are considerably more expansive than KBMAs.
Kernel-Based Urban Areas (KBUAs)
An alternative benchmark with more stringent criteria for combining locations. KBUAs are more compact than KBMAs and typically encompass a lower share of commuting flows.
Additional Materials
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