Ever notice how businesses in the same industry tend to clump together in one city or state? Take the auto industry in Detroit, for example, insurance in Connecticut, or medical technology in Minnesota. Economists and policymakers often take special note of these groups of related businesses. That's because they're linked to local jobs and higher salaries. Academics call them industry clusters, and they're the subject of a conference this week at the University of Minnesota's Humphrey School of Public Affairs. Tom Crann caught up with Lee Munnich, a senior fellow at the Humphrey School.