Key Finding: In cases that reached final written decisions or were substantively denied institution, about 50% of claims that were originally challenged in PGR petitions were cancelled or found unpatentable. The analysis includes decisions not to institute through 2017, and final decisions through 2018, in order to account for the fact that final decisions typically issue about one year after the institution decisions. Unlike IPR and CBM proceedings, PGR proceedings can only be initiated for patents having a claim with an effective filing date that is on or after March 16, 2013. The percentage of claims cancelled or found unpatentable increased from 38% at the end of 2017 to 50.1% at the end of 2018. However, the variance derives in part from the small sample sizes (186 new claims in 2018 vs. only 339 claims from inception through the end of 2017). Thus, it is difficult to draw conclusions at this time.