Charles Lemley, Kimberly Moore
Date Posted: 2003
One of the oddest things to an outsider about the United States patent system is that due to continuation practice it is impossible for the U.S. Patent and Trademark Office (PTO) ever to finally reject a patent application. Continuation applications have led to abuse of the patent prosecution process. They serve very little useful purpose, and what benefits they confer may be outweighed by their potential for mischief. In an effort to study the pervasiveness of continuation practice, we compiled an original dataset comprising 2,224,379 patents, every patent issued from 1976 through 2000. We found that while continuations are filed in 23% of all patent applications, patents based on continuation applications represent 52% of all litigated patents. Although continuations are used in a minority of all patents, it is the most important minority because it is the minority most likely to end up in litigation. We examine the efforts undertaken to control the problems associated with continuation patents (changing the patent term, publishing applications, prosecution laches) and find them insufficient. The world would probably be a better place if they were abolished. Recognizing, however, that the abuse of continuation practice is not as pervasive as some might think, we propose a number of means by which Congress and the courts could strengthen existing rules designed to limit their abuse while preserving the practice. At a minimum, the empirical data we present can provide litigants and judges with a baseline for assessing the reasonableness of delay caused by the filing of multiple continuations by the patentee in determining the applicability of equitable remedies such as prosecution laches.