I don't have a direct answer to your question, but I'd like to add this to the mix:

Rural regions without colleges tend to have populations focused on production, not R&D. Can these regions produce startups? Of course. But it won't happen in the quantities it does in urban areas.

I think the recipe for high quantity/quality startup production is: High population (populous areas will have more of everything, including startups), high education (startups require a R&D mentality), high salary (someone's got to pay for those startups), and high number of head offices (management experience).