Economics professor Stan Liebowitz has filed a rebuttal expert report in the upcoming Joel Tenenbaum file-sharing case, which aims to show that file-sharing does have a negative immpact on sales of recorded music. In fact, he argues that weakening of property rights is the main reason for the decline in recorded music sales, rather than any failure in business models or competition from other forms of media. “It is always possible to change one’s line of business, but when someone is forced to do so because property rights in their product are deteriorating, the forced change in business models indicates that the entity changing models has been harmed,” he writes.