The Economics of Patents and Copyrights, by French researchers Francois Leveque and Yann Meniere of the Ecole des mines de Paris (an engineering university), is available for free, under the Creative Commons License. It concludes (p. 102):

The abolition or preservation of intellectual property protection is … not just a purely theoretical quesiton. To decide on it from an economic viewpoint, we must be able to assess all the consequences of protection and determien whether the total favorable effects for society outweigh the total negative effects. Unfortunately, this exercise [an economic analysis of the cost and benefits of intellectual property] is no more within our reach today than it was in Machlup‘s day [1950s].

(Thanks for Greg Aharonian of PatNews for the link and some comments.)