Aditi Mehta (),
Marc Rysman () and
Tim Simcoe ()
Additional contact information Aditi Mehta: Department of Economics, Boston University
Tim Simcoe: J.L. Rotman School of Management, University of Toronto
Authors registered in the RePEc Author Service: Pierre Perron ()
Abstract:
Previous work studying the age distribution of citations for patents relies on functional form assumptions to address the co-linearity between the birth year, citation year, and age. This paper proposes a non-parametric identification strategy that uses the lag between application and grant as a source of exogenous variation. We show empirically that the “citation clock” starts only when a patent issues, and we examine the potential bias if our assumption is incorrect. We use our approach to re-examine some prior results on the citation age profile of patents from different technological fields. We discuss potential extensions into other research areas.