The Examination of Continuation Applications and the Problem of Invalid Patents in the U.S.

It has long been recognised that the U.S. patent office routinely grants a large number of invalid patents. Recently, scholars have studied the root causes of this issue and have emphasised the key role played by the patent examination process itself. In this paper, I study how features of the examination process affect examiner behaviour and the problem of invalid patents in the context of continuation applications. These applications emanate from earlier patent applications filed at the patent office and allow applicants to submit new claims for a given invention. In the U.S., continuations are generally examined by the same examiner who was assigned to the earlier application. Using application-level data, I explore how this feature, which I call "relatedness," affects examiners' grant decisions and other examination practices. I find that relatedness increases the grant rate, decreases examiners' efforts to narrow down the scope of protection claimed by patent applicants and decreases the examiners' search efforts for prior art. I also show that the effects of relatedness do not seem to be driven by a "wearing down" effect on examiners and differ only slightly across different technology areas. Finally, I find evidence that relatedness leads to the granting of patents of more dubious validity. A key implication of these results is that the way the U.S. continuation application system is designed causes examiners to adopt softer examination practices, which in turn contributes to the problem of invalid patents.