Revisions to the set of MAs have occurred in practically every year since 1950, most often to recognize an MA for a growing small city. However, the great majority of revisions in the metropolitan definitions have occurred on the basis of decennial census data. These census-based revisions have taken place two or three years after the census, too late to be reflected in most publications of that census. The time lag stems from the fact that commuting data from the census are a key ingredient for determining which counties qualify for inclusion. The question on place of work is part of the sample census questionnaire and is not processed immediately for that reason; in addition, the place-of-work responses must be coded to permit tabulation in terms of standard geographic areas.
After 1960, 1970, and 1980, OMB did recognize a number of new individual MAs soon after the census based on total population counts, and these new areas were reflected in the tabulations and publications of that census. Updating of existing areas then took place separately, in the third year after each of these censuses. In some cases, however, the new commuting data caused areas created in one year to be changed or even merged with others two years later. For this reason, OMB decided not to recognize any new areas in 1991 but to defer all updating until the 1990 commuting data could be reviewed. OMB's announcement of MA definitions based on 1990 data and standards was effective December 31, 1992.
Fewer MSAs and CMSAs.2 The total number of current MSAs and CMSAs in the U.S. is 268, 16 fewer than the number in effect for the 1990 census (Table 1). (The 275 MSAs and CMSAs of 1983 had increased by nine new areas to 284 by 1990.) The 1992 announcement expanded 16 CMSAs and MSAs by adding to them one or more formerly separate MSAs; 24 MSAs were folded into other areas in this way. The most notable of these combinations brought together a pair in many respects dissimilar, Washington and Baltimore, forming a metropolitan complex that ranks fourth in the nation in population. Boston expanded by adding no less than five previously separate MSAs.
Besides the mergers, another 56 areas added territory, while 13 areas lost territory, and seven both added and lost. Finally, nine new MSAs were established in 1992, and one area, Jackson, TN, was disqualified because it had been established based on a 1984 postcensal population estimate that was not confirmed by the 1990 census. The 18 new MSAs announced between 1984 and 1992 are in contrast to the more than 40 new areas established between 1973 and 1983, some of which reflected a broadening of the requirements for qualification.
There has been some trend on the part of the largest areas against becoming CMSAs with component PMSAs. The motivation seems to be the negative effects (perceived or genuine) for the core of the area to have a smaller population total as a PMSA than it would have if the whole area remained undivided as an MSA. The count of CMSAs reached its peak in 1983, when 22 of the 35 metropolitan areas of at least 1 million population had PMSAs. Four additional areas at that time could have had PMSAs identified but turned the option down. Two areas that did opt for PMSAs in 1983 quickly changed their minds and secured a return to MSA status the next year. As of 1992 there were 40 areas of more than 1 million 1990 population, of which 27 could have had PMSAs. There was no significant local support expressed for the option in nine cases, reducing the count of CMSAs to 18.
In the 1992 updating, 167 of the 284 areas of 1990, or 58.8 percent, had no change in boundaries, although some of these did have changes in titles or central cities. This is about the same share as in 1983, when 174 or 60.9 percent of the 286 areas of 1981 had no change in boundaries.
More MA components. There were 12 counties added to metropolitan territory from 1984 to 1990, nearly all as part of newly recognized MSAs. There were no changes in definitions in 1991. The 1992 additions to metropolitan territory consisted of 90 counties added to existing MAs (usually on the basis of strengthened commuting ties) and nine in newly established areas, plus 62 additions of cities and towns to the New England areas; 18 counties and three New England units dropped out. Although these changes increased the number of metropolitan component areas by more than 10 percent, the effect on metropolitan population was much smaller. Using 1990 census populations, the 1992 additions added 5.5 million population while the deletions amounted to 0.7 million, for a net increase of 4.7 million or less than 3 percent of the 1990 total metropolitan population.
Of the 90 counties added in 1992, 16 had been metropolitan previously but were dropped at an earlier date, most of them in 1983 when the rules for qualifying outlying counties were tightened somewhat. Generally, since their earlier deletion from MAs such counties have achieved higher population densities and/or higher commuting to cores sufficient to meet the specified thresholds for inclusion.
Geographic distribution of the inventory changes. Counties added to metropolitan territory since the last updating are scattered across much of the country rather than concentrated in any one region (Figure 1). The two largest concentrations of added counties reflect the expansion of the Washington-Baltimore area by eight counties and one independent city, and the Cincinnati area by five counties--one in Indiana, one in Ohio, and three in Kentucky.
That the five counties added to the Cincinnati area accounted for a smaller population than the single county added to Cleveland is a reminder of the variable geographic contexts of MAs. Besides Cincinnati and Cleveland, counties were added to several other Manufacturing Belt MAs, including Fort Wayne, Chicago, Detroit, Rockford, and St. Louis, even though none of these areas grew greatly in population during the decade; the Detroit and Cleveland areas, in fact, gained counties while losing population within constant boundaries.
The census division with the largest number of additions was the South Atlantic. Seven of the nine new MSAs announced in 1992 are in this division, with North Carolina and South Carolina accounting for five of the areas. In total, the South Atlantic division saw 28 counties added to existing MAs (including those added to the Washington-Baltimore area) and nine included in newly recognized MAs after 1983 (Table 2). However, four counties also dropped out of MAs in this division in 1992. The high counts of changes in this division in part reflect that its counties tend to be small in area. The Atlanta MSA, which already had 18 counties, added three more but lost one to bring its total to 20, more components than any other area outside New England except New York and Washington-Baltimore.
Additions to metropolitan territory in the West occur mainly when new MAs qualify. In this decade, however, a few geographically very large counties in the West have qualified for inclusion as outlying MA counties.
In a number of cases throughout the nation the additional counties have filled gaps in existing chains or groups of MAs. Additions in New York and Ohio established or widened connections between Syracuse, Rochester, Buffalo, Erie, and Cleveland. Metropolitan counties are now continuous from the Greenville-Spartanburg-Anderson MSA in western South Carolina to the Greenville MSA in eastern North Carolina. With the exception of two counties, MAs occupy the entire Florida coast from Jacksonville south and then north on the Gulf Coast past Tampa. Establishment of a new MSA comprising San Luis Obispo County, hitherto the largest nonmetropolitan county in the country, completed continuous coverage of the California coast from the Mexican border to well north of San Francisco. However, as persons familiar with any of these areas will recognize, the fact that county-defined MAs are continuous is by no means the same as saying that urbanization or even suburbanization is continuous in these areas.
Of the 4.7 million net increase in 1990 MA population accounted for by the areas added in the 1992 announcement, 0.7 million was in the Northeast, 1.0 million in the Midwest, 0.8 million in the West, and 2.2 million in the South.