Abstract: Copyrights grant publishers exclusive rights to content for almost a century. In science, this can involve substantial social costs by limiting who can access existing research. This column uses a unique WWII-era programme in the US, which allowed US publishers to reprint exact copies of German-owned science books, to explore how copyrights affect follow-on science. This artificial removal of copyright barriers led to a 25% decline in prices, and a 67% increase in citations. These results suggest that restrictive copyright policies slow down the progress of science considerably.