The duration of copyright increased under U.S. law in several steps since the eighteenth century until it reached the life of the author plus 70 years. Suppose that a writer completes a novel at age 40. If the writer lives to be 75, then the copyright will last for 105 years. At an interest rate of 10%, the present value of $1 paid after 105 years equals much less than 5 cent. What does this fact suggest about whether the efficient duration of copyright is longer or shorter than currently provided by law?