The page on this link will give you summarized information on a recent study conducted in Minnesota on the economic impact of having artists in a community.  Studies like this one have been conducted before, but I have only heard them from places like NYC, not from an entire state.

http://www.mtn.org/mca/

"The Findings of a 2007 study documented in unprecedented scope and detail the annual economic impact of Minnesota's individual artists. Seven studies were produced, including six regional and one statewide report, which explored both the economic impact of artists and looked at their access to health care and retirement plans. "  Minnesota Citizens for the Arts