Patents are supposed to disclose technical information in order to facilitate subsequent inventions. This argument has found only scant attention with economists, but has been highly relevant in legal reasoning. To date there is no quantitative evidence evaluating the impact of patent disclosures. This paper uses responses from a large-scale inventor survey. Inventors were asked about the time savings due to their knowledge of the patent literature. Time savings from disclosures follow a highly skew distribution with a median of 3.5 hours and a mean value of 15 hours per patent. The overall social value of patent disclosures in the European patent system is very small in comparison to the private value of patents.