PLOS One recently published a paper and a set of maps that looks at commuter flows across the United States (over 4 million data points). The objective was to identify all of the country’s “megaregions.”
Here is one of those maps. I think it says a lot.
We often think of cities as having discrete boundaries and population counts, but the reality is that studies and maps such as these provide a much better sense of the overall economic geography of a place.
It’s worth noting that the commuter dataset used for this study is from 2006-2010. So things may look a bit different today. The full report can be found here.