A core-based statistical area (CBSA) is a geographic region of the U.S., as defined by the Office of Management and Budget (OMB) in 2000.
CBSAs are either urban or rural. There are micropolitan or metropolitan areas within the urban category, encompassing densely populated residential, non-residential and commercial land. Micropolitan areas have a population of 10,000 to 50,000 people in an urban cluster, while metropolitan areas have one or more urban centers and a population of at least 50,000 people.
CBSAs are re-classified every census with a combination of data and census information.