So says mathematics (thanks, D)
[Rufus] Pollock’s work is based on the pr[e]mise that the optimal level of copyright drops as the costs of producing creative work go down. As it has grown simpler to print books, record music, and edit films using new digital tools, the production and reproduction costs for creative work in have dropped substantially, but actual copyright law has only increased.
The result? An optimal copyright term of 14 years, which is designed to encourage the best balance of incentive to create new work and social welfare that comes from having work enter the public domain (where it often inspires new creative acts).
This is exactly what Michael Hart and I have been arguing (him in papers, me on listservs) for years, but now with proof and a not-so-round number.