“. . . if one decides that the entire Chicagoland should be considered as one unit, then Ann Arbor should be considered as part of the extended Detroit area.”
That’s just silly. The survey is based on MSAs as defined by the Census Bureau. The entire Chicago metropoitan area–city plus suburbs—is a single MSA, and for good reason. Detroit and Ann Arbor are not part of a single MSA; each has its own MSA based on their own distinct economies and employment, commuting, and residential patterns. It’s just an objective fact that the Chicago MSA is economically and socially one integrated unit, while Detroit + Ann Arbor are not a single integrated unit, not by any stretch.
Chicago and its suburbs operate as a unified whole. The suburbs are in part bedroom communities for people who work in the city, while others reverse commute, living in the city and working in the suburbs. The suburbs are also major employment centers in their own right, but they largely employ people in businesses and institutions that are themselves closely integrated with the economy and institutional fabric of the city.
Detroit and Ann Arbor simply don’t have that kind of close relationship. Relatively few people dommute between the two, though there are a handful. Detroit is still primarily a manufacturing center relying heavily on the auto industry, while Ann Arbor has more of a post-industrial knowledge-based economy that interacts with Detroit’s older manufacturing economy only tangentially. Some of the R&D that takes place in Ann Arbor benefits the auto industry, but in some ways Ann Arbor’s economy is more closely tied to Chicago than to Detroit.
Roughly half the University of Michigan’s undergraduates come from metro Detroit, which only makes sense because it’s by far the largest population center in the state, with about half the state’s population. But Michigan’s graduate students actually outnumer undergrads, and only a small fraction of themcome from metro Detroit. And far more Michigan alums end up in Chicago than in Detroit simply because their skills and talents are more in demand in Chicago’s more diversified and more knowledge-based economy. If we’re going to go beyond standard MSA boundaries as defined by the government, it might make more ense to conside Chicago and Ann Arbor as a single unit than Detroit and Ann Arbor.