Beginning in the early 1980s, the U.S. Government reformed the patent law in ways that made patents easier to acquire and defend, but further efforts to expand the rights of patent owners had stalled by the mid-1990s. I use a political economy model to explain these changes in terms of the shifting constituency interests represented by members of the U.S. Congress. As the distribution of patenting became less skewed in the 1980s, more members represented constituencies likely to benefit from inefficient patent policy. But as the distribution of patent holding became more skewed once again in the later 1990s, support for expansions of patent rights decreased.