I do a fair amount of work tracking brand name mentions. On thinking about this post and the others at PDD that track Duluth references in pop culture, I think there's a strong anecdotal consensus that Duluth is overmentioned relative to it's share of the U.S. (or maybe predominantly English-speaking) population. 

A neat project that I will tackle at some time is to use Google books ngram as a broad sampling of mentionshare and track mentions of "Duluth" relative to populationshare over time alongside a representative sample of other cities. Following the anecdotal evidence, I suspect that Duluth captures disproportionate mentionshare relative to populationshare. I also suspect that Duluth's current mentionshare is close to what would be expected for Duluth's populationshare in the early 20th century; i.e. our prominence in pop culture remains pegged to that incandescent period.