During the 1990s, the Office of Management and Budget (OMB) established and led the Metropolitan Area Standards Review Project with the purpose of reviewing and, if necessary, revising the 1990 metropolitan area standards. The project culminated in new standards for the first decade of the 21st century.

The December 27, 2000 Federal Register included a notice (see below) announcing OMB’s adoption of Standards for Defining Metropolitan and Micropolitan Statistical Areas. These standards replaced and superseded the 1990 standards for defining metropolitan areas. The new standards reflected decisions reached by OMB on recommendations by the interagency Metropolitan Area Standards Review Committee and in response to public comment on those recommendations. OMB applied the new standards to Census 2000 data and announced area definitions on June 6, 2003.

The approaches presented in the Federal Register Vol. 63, No. 244 drew upon work that began in the first half of the 1990s with four commissioned studies suggesting alternative approaches to defining metropolitan and nonmetropolitan areas. These studies were published in September 1995 by the Census Bureau’s Population Division as Working Paper No. 12, Metropolitan and Nonmetropolitan Areas: New Approaches to Geographical Definition.