A Survival Analysis of the Approval of U.S. Patent Applications

We model the length of time that it takes for a patent application to be granted by the U.S. Patent and Trademark Office, conditional on the patent actually being awarded eventually. Survival analysis is applied and both the nonparametric Kaplan-Meier and parametric accelerated failure time models are used to analyze the data. We find that the number of claims a patent makes, the number of citations a patent makes, the patent’s technological category, and the type of applicant all have significant effects on the duration that a patent is under consideration. A log-normal survival model is the preferred parametric specification, and the results suggest that the hazard function is non-monotonic over time.