This article aims at estimating the optimal profile of renewal fees patent offices should implement. It is at the crossroad of two strands of literature. The first strand is the theoretical literature analysing renewal fees as an optimal revelation mechanism. The second strand is the econometric literature developing real option models of patent renewal decisions to assess the value of patents. Using data from the French patent office, we find that there is little room to lower the social cost of patents without affecting the monetary incentives to apply for a patent and innovate. We show that a menu of optimally defined profiles helps to further discriminate among patents