A Heretical View of File Sharing:
"But what if the industry is wrong, and file sharing is not hurting record sales?

It might seem counterintuitive, but that is the conclusion reached by two economists who released a draft last week of the first study that makes a rigorous economic comparison of directly observed activity on file-sharing networks and music buying.

'Downloads have an effect on sales which is statistically indistinguishable from zero, despite rather precise estimates,' write its authors, Felix Oberholzer-Gee of the Harvard Business School and Koleman S. Strumpf of the University of North Carolina at Chapel Hill.… "

http://www.nytimes.com/2004/04/05/technology/05music.html