Arbitron Metro Survey Areas generally correspond to the federal government's Metropolitan Areas.

A Metropolitan Area includes a city (or cities) whose population is specified as that of the central city together with the county or counties in which it is located. Metropolitan Areas may also include additional or contiguous counties when their economic and social relationships meet the criteria specified for metropolitan integration. Commuting, population density, urbanization and other data supplied by the U.S. Bureau of the Census are used to define Metropolitan Areas. A Metropolitan Area may cross state lines.

Metropolitan Areas can stand alone, in which case the designation is simply Metropolitan Statistical Area (MSA); or they can be large metropolitan areas composed of smaller metropolitan areas, where both the whole and each component area qualify as "metropolitan" according to the standard guidelines. The individual metropolitan areas which comprise the larger Consolidated Metropolitan Statistical Area (CMSA) are designated Primary Metropolitan Statistical Areas (PMSAs). MSAs and PMSAs, which are the basic (non-overlapping) metropolitan units, are most frequently used by businesses and other users of census data, although some of Arbitron's radio Metros do conform to the CMSA definitions.

For areas that do not have an OMB defined metropolitan area, Arbitron usually defines the Metro Survey Area to include the county(ies) of the majority of the local area radio stations' city(ies) of license. Arbitron Metro Survey Areas may cross state lines.

Although in most cases radio Metros are defined in terms of whole counties, in some cases (notably New England, (4) but elsewhere, as well), it may be necessary for Arbitron to subdivide a county into two or more split counties in order to accommodate within-county variations in signal reception and/or radio listening patterns. Split counties are defined and maintained at the zip code level, and are treated as separate sampling units for purposes of Metro Survey Area definition, sample placement and returned-sample weighting.

Arbitron Metro Survey Area definitions are reviewed for possible update once every 10 years, after the OMB has updated its Metropolitan Areas based on the new decennial census data. In the review process, consideration is given to longstanding historical definitions. Planned changes are announced in advance so that consideration may also be given to the views of subscribers.

Changes to existing Metro Survey Area definitions between the 10-year OMB review cycles will be considered by Arbitron if a formal written proposal, which presents in detail the rationale and benefits of the proposed Metro, is submitted to Arbitron within established deadlines; widespread subscriber support for the change is generally required, as well.