That is the term describing metro areas and this article from New Geography is chock full of new and interesting data; Sacramento comes in at 25 on the longer chart.
Core Based Statistical Area (CBSA) is the Office of Management and Budget’s (OMB) way of defining metropolitan regions. The OMB (not the Census Bureau) defines criteria for delineating its three metropolitan concepts, combined statistical areas, metropolitan statistical areas, and micropolitan statistical areas. The CBSA has obtained little use since this adoption for the 2000 census. According to OMB:
“A CBSA is a geographic entity associated with at least one core of 10,000 or more population, plus adjacent territory that has a high degree of social and economic integration with the core as measured by commuting ties.”
In this context, core means urban area. If an urban area has 50,000 or more population, OMB defines a metropolitan area around it. If an urban area has 10,000 or more population but fewer than 50,000 residents, OMB defines a micropolitan area around it.
It is also important to understand that CBSAs, whether CSAs, metropolitan areas, or micropolitan areas are not urban areas. In fact, 94% of the area in CBSAs is rural — only 6% is urban (built-up urban cores and suburbs).
Combined statistical areas (CSAs) are made up of adjacent CBSAs that have a significant amount of commuting between them, but less than required for a metropolitan area or a micropolitan area. In some cases the CSAs seem so obvious as to make the smaller metropolitan area definitions seem ludicrous. One keen observer, Michael Barone of the Washington Examiner, put San Francisco and San Jose, as well as Los Angeles and Riverside-San Bernardino together in his recent analysis of population growth, because, as he rightly pointed out, they seem to “flow together.”
Some CSAs are very large. For example the New York CSA is composed of 8 metropolitan areas (New York (NY-NJ-PA), Bridgeport (CT), New Haven (CT), Trenton (NJ), Allentown (PA-NJ), Kingston (NY). Torrington (CT) and East Stroudsburg (PA). On the other hand, many major metropolitan areas are not a part of a CSA, such as Phoenix and San Diego.
Since the term CBSA seems unlikely to achieve popular usage, this article uses the term “commuter shed” to denote the highest local level of metropolitan definition. The highest level for the largest regions are is the combined statistical area (CSA). In others they are defined as a metropolitan area or micropolitan area. The result is a consistent standard of economic geography defined by commuting. Yet such lists are rare or non-existent. A table of all 569 commuter sheds (over 1,000,000 population) is posted to demographia.com.
Retrieved June 23, 2015 from http://www.newgeography.com/content/004965-americas-largest-commuter-sheds-cbsas