PATENTS ARE a powerful tool for asserting intellectual property rights—they offer innovators profitable exclusive rights, thereby providing incentive for critical (and costly) investments in research and development. However, this exclusivity is limited in time. After 20 years (from application), patents expire and generic producers can practice the invention. The enhanced competitiveness of the market typically brings additional Patent Expiration, Product Concentration, and Glyphosate Use: A Tale of Unexpected Consequences by GianCarlo Moschini, Edward Perry, and David Hennessy moschini@iastate.edu; edperry@ksu.edu; hennes64@msu.edu benefits to final users. Not much is expected to go wrong when a critical patent on a major product expires— but, as articulated in a recent CARD study (http://bit.ly/CARD19wp588), glyphosate provides an unusual tale.