Park City, Utah has two ski resorts that both call themselves the biggest thing to happen to skiing there in decades. Neither one is owned by anyone who lives there.

By 2005, real language-processing companies existed in Las Vegas, a Boston suburb, Pittsburgh, and a small city outside Salt Lake City -- not one of them in Silicon Valley. Each was funded independently, wherever it already existed, by capital chasing one urgent national need.

Three competing explanations for why a specific activity clusters in a specific place -- geography, government, and personal preference -- and which one actually carries the weight in two real cases.