[sanderjd]

Very possibly it has - there is no way to know the answer to this kind of what-if, because you either have one or you have the other, you can't let the two alternatives compete with each other over the same time scale and then measure the outcomes. Very similar to the question of whether software patents help or hurt software innovation. There has been innovation in engineering with the PE system in place, and there has been innovation in software with the patent system in place, but there is no way to know if there would have been more or less over the same time period without those controls.