With the push for a taxpayer-subsidized minor-league baseball stadium in Providence continuing, this quotation from a 2012 essay in The Atlantic seems like something worth keeping handy (emphasis added):

… according to leading sports economists, stadiums and arenas rarely bring about the promised prosperity, and instead leave cities and states mired in debt that they can’t pay back before the franchise comes calling for more.

“The basic idea is that sports stadiums typically aren’t a good tool for economic development,” said Victor Matheson, an economist at Holy Cross who has studied the economic impact of stadium construction for decades. When cities cite studies (often produced by parties with an interest in building the stadium) touting the impact of such projects, there is a simple rule for determining the actual return on investment, Matheson said: “Take whatever number the sports promoter says, take it and move the decimal one place to the left. Divide it by ten, and that’s a pretty good estimate of the actual economic impact.”

Others agree. While “it is inarguable that within a few blocks you’ll have an effect,” the results are questionable for metro areas as a whole, Stefan Szymanski, a sports economist at the University of Michigan, said.