Intellectual Property Rights (IPR) regimes for plant breeding are generally justified on the basis that they encourage innovation. Introduction of IPR regimes for plant varieties in the United States has led to increased concentration, but it is less clear whether IPRs have promoted useful innovation, as measured by productivity of available corn hybrids. There are difficulties in finding a satisfactory measure of innovation in plant breeding, and in this paper we propose a procedure. Results from the annual corn hybrid trials conducted by 11 US universities over the 20 years from 1990 to 2009, at 365 separate locations in the 11 states, have been collated. This set of unbalanced panel data for grain corn hybrid trials has been used in a fixed effects... |