The Factors Related to the Minimum and Maximum Survival of Patents against Challenges to Validity

In order to shed new light on the methodology of empirical studies on factors relating to patent validity, this study uses criteria based on the difference of the scope of protection at the time of grant and after the challenge as the dependent variable, and includes some new and recently studied independent variables related to the patent application and prosecu-tion. Thus, 267 Japanese patents with application dates between October 2001 and De-cember 2004 which were subsequently challenged in invalidation trials were categorized into three outcomes; (1) “complete survival”, (2) “partial survival” and (3)“complete loss”. Groups (1)+(2) and (3), or groups (1) and (2)+(3) were compared using logistic regression analysis to identify factors relating to the minimum and maximum survival of patents, re-spectively. The results showed a different set of variables significantly correlating with the minimum and maximum survival, indicating differences in the qualitative impacts of the variables on patent validity. Policy implications are also considered.