The sad thing is, in order to conclusively attribute economic impact to public art you have to set up a situation where you measure your indicators pre-investment and then measure at several intervals post-investment, trying to control for other variables.  It’s really difficult to separate out just the impact of public art because usually it’s part of a package of other investments.  I’d really love for someone to set up a very strictly controlled study of 2 identical neighborhoods, one which gets ONLY public art and the other gets nothing, and then measure for a period of like 5 years, since it often takes time for the impact to be felt and then measured.

Having said all that—very limited studies have been done but they are not conclusive and they are specific to that locale.  I’ve attached an old article about how public art stimulates economies that could provide some information, and a couple of other articles I’ve saved over the years.