A metropolitan or micropolitan statistical area's geographic composition, or list of geographic components at a particular point in time, is referred to as its "delineation." Metropolitan and micropolitan statistical areas are delineated by the U.S. Office of Management and Budget (OMB) and are the result of the application of published standards to Census Bureau data. The standards for delineating the areas are reviewed and revised once every ten years. Generally, the areas are delineated using the most recent set of standards following each decennial census. Between censuses, the delineations are revised to reflect Census Bureau population estimates and--once each decade--updated commuting-to-work data. Areas based on the 2020 standards and Census Bureau data were delineated in July of 2023.
Related statistical areas include combined statistical areas, which are aggregates of adjacent metropolitan or micropolitan statistical areas that are linked by commuting ties; and metropolitan divisions, which are a county or group of counties (or equivalent entities) delineated within a larger metropolitan statistical area, provided that the larger metropolitan statistical area contains a single core with a population of at least 2.5 million and other criteria are met.