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 UA. In many instances, the decision hinges on the location of the UAs within metropolitan areas (MAs).

The MAs are geographic entities established by the Federal Office of Management and Budget (OMB). The general concept of an MA is that of a core area containing a large population nucleus, together with adjacent communities that have a high degree of economic and social integration with that core area. The fundamental geographic units of MAs are counties, except in New England, where they are cities and towns.

The term MA is a collective one; individual MAs are metropolitan statistical areas (MSAs), consolidated metropolitan statistical areas (CMSAs), or primary metropolitan statistical areas (PMSAs). Qualification as an MSA requires the presence of a city of at least 50,000 population, or a UA and a total population of at least 100,000 (75,000 in New England). The MSA’s geographic extent is a function of commuting patterns and other specified characteristics such as population density. Within an area that qualifies as an MSA and also has a population of one million or more, individual component areas are identified if specified criteria are met and local opinion supports separate identification. These component areas are designated PMSAs, and the entire area containing the PMSAs is designated a CMSA. If no PMSAs are defined, the entire area is designated an MSA. (For further information on MAs, see, “Metropolitan Areas.”)

Contiguous UAs maintain their separate identity when: The Census Bureau generally merges contiguous UAs when major portions of the UA territories are located in the same MSA or PMSA. In addition, all of the following conditions must be present:
 * The UAs are entirely or mostly in different MSAs or CMSAs.
 * The major portion of the UA territory is in the same CMSA but in different PMSAs.
 * The largest central place of one UA is mostly outside of the MA that encompasses the other UA.
 * There is continuous development, with no more than one jump in each {{left|12-12{{gap}}Urban and Rural Classifications