Movie Welfare Bleg:

Many states and nations have begun offering "incentives" (corporate welfare) for movie-making in their jurisdiction. The subsidies are commonly justified on the grounds that they help the local economy. Do any readers know of any studies assessing to what degree, if any, film industry subsidies actually do benefit the economy of the subsidy-giver? If you have answers (not just speculation), please supply them in the Comments. Thank you.