A study released last week by Harvard and UNC researcher states that "downloads have an effect on sales which is statistically indistinguishable from zero." This has, of course, been met with some disbelief by the RIAA. A New York Times article discusses the study and the music industry's reaction. The most recent findings are in keeping with what most people learned in Economics:

"Say I offer you a free flight to Florida," he asks. "How likely is it that you will go to Florida? It is very likely, because the price is free." If there were no free ticket, that trip to Florida would be much less likely, he said. Similarly, free music might draw all kinds of people, but "it doesn't mean that these people would buy CD's at $18," he said.

From A Heretical View of File Sharing
Referenced Mon Apr 05 2004 08:33:11 GMT-0600

The study hasn't been peer reviewed yet, but several other scientists have commented that the technique looks to be sound. I'm sure that facts will just confuse the public policy debate.

BTW, you'll notice that I've taken pains to avoid the use of the term "file sharing" in discussing this since I think that using that term unnecessarily confuses the issue and hurts legitimate uses of P2P technology.