A recent post of mine, pointed out that by 2018, the Washington-Baltimore Combined Statistical Area (CSA) would likely have more people than the Chicago-Naperville CSA. It elicited several responses including that the analyses was pointless because CSA is a meaningless measure – what matters are MSAs (Metropolitan Statistical Areas).
This critique is not new but it reminded me that many are skeptical of CSAs and that how we define (and measure) an integrated urban area, and compare it against others, is both important and contentious.
First, what do we mean by MSA and CSA?
An MSA, as defined in 2010 by the Office of Management and Budget (OMB), is an area “associated with at least one urbanized area that has a population of at least 50,000” and it includes the jurisdiction(s) containing the core “plus adjacent outlying counties having a high degree of social and economic integration with the central county or counties as measured through commuting.”
A CSA, also defined in 2010 by the OMB, is “A geographic entity consisting of two or more adjacent [MSAs or micropolitan statistical areas] with employment interchange measures of at least 15.” Employment interchange measure “is the sum of the percentage of workers living in the smaller entity who work in the larger entity and the percentage of employment in the smaller entity that is accounted for by workers who reside in the larger entity.”
So basically, a CSA must meet two qualifications:
- There must be two MSAs adjacent to each other, and
- They must have interconnected labor markets.
Which is more meaningful?
An MSA usually defines a smaller, more compact, and more integrated area and, as such, is a very useful tool for statisticians, demographers, politicians, and businesspeople to make sense of a broad urban area. However, CSAs can also be useful, albeit often less so, because they describe an even broader urban area that typically is more sprawling and less interconnected. Nonetheless, CSAs can describe an urban region that has significant ties – ties which are more meaningful than two entirely distinct MSAs (e.g. Philadelphia and New York City). In a similar way, it’s helpful (albeit with significant limitations) to conceptualize the Boston-New York-Washington northeast corridor as one megalopolis – this level of analysis does not have its own OMB definition due to its comparably much weaker interconnections.
So in the end, its opinion that matters
While we have objective measures to define MSAs and CSAs, ultimately, whether either measure is meaningful depends on the person and their perspective. For example, while people who live in Baltimore and work in D.C. may agree that the two MSAs are well integrated, a person who lives and works in the far reaches of the Northern Virginia suburbs may be significantly less convinced.
For a more detailed discussion of the advantages and disadvantages of various levels of analyses, see this article from Transport Politic.
Source for map: US Census Bureau