This article defines a "primary" metropolitan area as a metropolitan area that is not a component of a more extensive defined metropolitan area. The 574 primary statistical areas (PSAs) of the United States and Puerto Rico comprise all 169 Combined Statistical Areas (CSAs) currently defined by the United States Office of Management and Budget (OMB) and the 405 of 929 Core Based Statistical Areas (CBSAs) currently defined by the OMB that are not a component of a Combined Statistical Area.