New research by Joel Waldfogel shows that the erosion of copyright does not necessarily lead to worse products. The study "Copyright Protection, Technological Change, and the Quality of New Products: Evidence from Recorded Music since Napster", published in the Journal of Law and Economics (working paper version), assesses the quality of recorded music since Napster.
Three different approaches are used (critics’ lists, music sales, and airplay data), assuming that if the music is better, it should be sold or played more often. Contrary to my own view, there is no evidence that the music released since Napster was of lesser quality. Copyright protection should therefore be weighted against producer surplus and consumer surplus.