Patents add ‘the fuel of interest to the fire of genius’. These words, attributed to Abraham Lincoln,1 appropriately capture the economic perspective of patent grants. The patentee receives a legal monopoly2 permitting him to charge prices above competitive levels, simply because the competition cannot resort to imitation (always an obvious competitive means) but must find substitutes for the patented product. In theory, there is nothing objectionable in that. The very existence of a patent system would seem to imply that above-market compensation must be available to a successful innovator.