The copyright industries—such as music, film, software and publishing—occupy a significant and growing share of economic activity. Current copyright law protects the creator for up to 70 years after their death, significantly longer than patent protection (20 years after invention). Copyright law aims to balance the incentive to create new work against the costs associated with high prices and restricted access to this work. This paper reviews the economic issues behind copyright and how these are challenged by changes in technology and market structure. While economics provides a powerful conceptual framework for understanding the trade-offs involved, the paper argues that our empirical knowledge base is very weak. Much more empirical analysis is needed to understand the impacts of changes to copyright legislation. Without such analysis, policy and legal debates will continue to be based largely on anecdote and rhetoric.