Comparison of examiners’ forward citations in the United States and Japan with pairs of equivalent patent applications

In this study, we investigate and compare the number of examiners’ forward citations in the United States and Japan. The most effective way to do so is to compare pairs of patent applications that have equivalent content. Therefore, we propose a new method of extracting substantially equivalent pairs of US and Japanese patent applications, focusing on the equivalence of the specifications and the claims. Our results reveal that during the substantive examination, US examiners cite patent application publications (PAPs) as well as granted patent publications (GPPs), whereas Japanese examiners tend to cite PAPs only. We further examine why GPPs are frequently cited by US examiners. The most likely reason seems to be that many US examiners retain the old habit of searching and citing only GPPs, but not PAPs. The insights offered by this study could be significant for future analyses based on the number of citations, particularly in the United States.