Why do many college towns have such a large sphere of influence? What affects how extensive it is?

[pikachu]

I wouldn’t put Princeton in the same category as Ann Arbor and Madison. While it matters to the local economy, it doesn’t have the associated hospital system that causes the economic dominance that Tintrlvr alludes to. (RWJ, which is associated with Rutgers, is more dominant.)

Big pharma is a bigger influence on the region’s economy, and the state government is also a major employer that is culturally ways away from Princeton. A lot of people also just live around Princeton because it’s a straightforward commute to NYC. The demographics of Princeton’s surrounding cities  are a tell - it’s a combo of Asian ethnoburbs, Trenton, and bronz-populated suburbia, not the type of places that you’d associate with a university.