Empirical research suggests strongly that copyright law—or at least excessive term length—has a negative effect on the public availability of works. Books, for example, become more available when they fall into the public domain. Also, follow-on works, such as audiobooks, are created at a higher rate after the underlying work falls into the public domain. In addition, for the most popular works, copyright is associated with significantly higher prices, which affects accessibility. Empirical evidence of other copyright-related market constraints is presented.