If you want to dig deeper into this, I suggest reading "The Clustering of America", by Michael J. Weiss. I think some of the key indicators it used were number

If you want to dig deeper into this, I suggest reading "The Clustering of America", by Michael J. Weiss. I think some of the key indicators it used were number of bowling alleys, liquor stores, and payphones (keep in mind, it was published in 1989).