Citation Weighting, Patent Ranking, and Apportionment of Value for Standard-Essential Patents
In patent-infringement litigation involving standard-essential patents, one must apportion the value of the patents in suit by deriving an appropriate measure of each patent’s value relative to the value of other patents that are also declared essential to the standard. Using data on patents declared essential to the LRDIMM standard, we have analyzed multiple methodologies that purport to measure the relative value of patents. We conclude that the choice of a particular patent-valuation methodology is secondary to the apportionment inquiry. In other words, we find that the particular weighting method that a researcher chooses to use is of secondary importance to the researcher’s decision to use some weighting method, rather than none. A simplistic patent-counting methodology that assigns each patent equal value relies on assumptions that are rarely satisfied in the real world. It produces a result that meaningfully differ from the results of any of the methods that rely on forward citations to measure a patent’s value.
We propose a half-life citation-weighting method that researchers might decide to use, in addition to adjustments for technology fields or unweighted citation counts. By placing greater weight on more recent citations, our proposed method attempts to account for the increasing number of citations and patents over time and the importance of speed during the standard setting process. Our proposed method might be particularly appropriate for standards in which the declared-essential patents cover similar technologies or in cases where innovation (and, consequently, the standards-development process) occurs rapidly.