Previous papers have demonstrated the link between these characteristics and the number of patent litigations. Next, we match our databases to the Stanford IP litigation database in order to obtain the number of litigations per patent. This database contains data on more than 100,000 intellectual property cases filed from January 2000 to the present. The lack of historical data pre-2000 could create a truncation problem for those patents granted before 2000. To control for this potential bias, we also run our regressions on patents granted during or after 2000 and for which we have all the history.

Henry Delcamp, Coordination mechanisms around ICT standardization projects: Four empirical essays on patent pools and consortia, (2011)