Combined statistical area

A combined statistical area (CSA) is composed of adjacent metropolitan (MSA) and micropolitan statistical areas (µSA) in the United States and Puerto Rico that can demonstrate economic or social linkage. 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 is that the social and economic ties between the individual MSAs within a CSA are at lower levels than between the counties within an MSA. CSAs represent multiple metropolitan or micropolitan areas that have an employment interchange of 25. CSAs often represent regions with overlapping labor and media markets.

As of July 2012, there are 169 combined statistical areas in the United States, plus three in Puerto Rico.