US CSAs

Combined statistical area (CSA) is a United States Office of Management and Budget (OMB) term for a combination of adjacent metropolitan (MSA) and micropolitan statistical areas (µSA) across the 50 US states and the territory of Puerto Rico that can demonstrate economic or social linkage. CSAs were first designated in 2003.[1][2] The OMB defines a CSA as consisting of various combinations of adjacent metropolitan and micropolitan areas with economic ties measured by commuting patterns. These areas that combine retain their own designations as metropolitan or micropolitan statistical areas within the larger combined statistical area. The primary distinguishing factor between a CSA and an MSA/µSA is that the social and economic ties between the individual MSAs/µSAs within a CSA are at lower levels than between the counties within an MSA.[3] CSAs represent multiple metropolitan or micropolitan areas that have an employment interchange of at least 15%.[3] CSAs often represent regions with overlapping labor and media markets. As of 2021, there are 172 combined statistical areas across the United States, plus another three in the territory of Puerto Rico.