JEL Class: D23, D42, D45, L41, L43, O34, O38 Patent Informatics for Patent Thicket Detection: A Network Analytic Approach for Measuring the Density of Patent Space Gavin Clarkson † I. Introduction...........................................................................................................................................1 II. Background ...........................................................................................................................................4 A. The Problem of Patent Thickets ........................................................................................................4 B. Prior Research on Patent Thickets and Patent Pools .........................................................................4 III. Patent Thicket Questions ......................................................................................................................6 A. Existence of a Patent Thicket ............................................................................................................7 IV. Objective Thicket Identification ...........................................................................................................9 A. Exploring Patent Networks ...............................................................................................................9 B. Deriving Patent Network Density ...................................................................................................10 C. Applying Patent Network Density...................................................................................................12 D. Identifying the Existence of a Patent Thicket ..................................................................................14 V. Examining Patent Pools ......................................................................................................................18 A. Sample Pools ...................................................................................................................................19 B. Analytic Comparison.......................................................................................................................19 C. Analytic Conclusions ......................................................................................................................24 D. Likelihood of an Alternate Outcome ...............................................................................................25 VI. Discussion ...........................................................................................................................................27 A. Contributions ...................................................................................................................................27 B. Limitations ......................................................................................................................................28 VII. References...........................................................................................................................................30 Abstract When organizations in technology industries attempt to advance their innovative activities, they may encounter patent thickets, or dense webs of overlapping intellectual property rights owned by different companies that must be hacked through in order to commercialize new technology. Throughout the last 150 years, however, organizations have stumbled into a number of patent thickets and have occasionally responded by constructing patent pools or organizational structures where multiple firms collectively aggregate patent rights into a package for licensing, either among themselves or to any potential licensees irrespective of membership in the pool. Such collaboration among technologically competing firms, however, has often encountered difficulty from an antitrust standpoint, even if the formation of the pool is pro-competitive. Despite all that has been written lamenting the problem of patent thickets, the antitrust regime has never had an objective method of verifying the existence of a patent thicket in a given section of patent space. In response to the lack of such a methodology, this paper proposes a tool to facilitate objectively demonstrating the existence of patent thickets. This paper proposes a thicket identification methodology that uses a network analytic technique to determine if a patent pool is coincident with a patent thicket by comparing the density of the patent pool to the density of the surrounding patent space. This paper then applies the new methodology to two existing patent pools and verifies the existence of underlying patent thickets. † Assistant Professor, University of Michigan School of Information, School of Law, and Native American Studies. This research was supported by the National Science Foundation under Grant No. IIS 0425116 as well as by two fellowships from the Harvard Law School: the John M. Olin Research Fellowship in Law, Economics, and Business and the Reginald F. Lewis Fellowship for Law Teaching. Research assistance was also provided by University of Michigan School of Information doctoral student Cory P. Knobel, who assisted in the data analysis and provided numerous helpful comments that are incorporated into the various discussions of network analytics in patent space. I am of course indebted to the members of my doctoral thesis committee at the Harvard Business School, Connie Bagley, Clay Christensen, Joe Kalt, and Josh Lerner, for their guidance and mentoring in the development of this paper.