Studying P2P Studies

Rufus Pollock evaluates 5 empirical studies of P2P file sharing and its effect on music purchasing: P2P, Online File-Sharing, and the Music Industry: "The basic result is that online illegal file-sharing does have a negative impact on traditional sales. The size of this effect is debated, and ranges from 0 to 100% of the sales decline in recent years, but a figure of between 20 and 40% would be a reasonable consensus value (i.e. that file-sharing accounted for 20-40% of the decline in sales not a 20-40% decline in sales)."