One of the oddest things about the United States patent system is that it is impossible for the U.S. Patent and Trademark Office (“PTO”) to ever finally reject a patent application. While patent examiners can refuse to allow an applicant’s claims’ to ownership of a particular invention, and can even issue what are misleadingly called “Final Rejections,” the patent applicant always gets another chance to persuade the patent examiner to change her mind. Even stranger, perhaps, is that the PTO doesn’t even possess the power to finally grant a patent.

Even when the examiner concludes that an invention is patentable and issues a “notice of allowance,” the patent applicant always retains the right to abandon the application that was deemed patentable and start the process over again. Alternatively, an applicant can take the patent awarded by the PTO and, at the same time, seek additional or broader claims arising out of the same patent application. In all three cases, the culprit lies in what is known as the “continuation” application. Applicants dissatisfied with the course of patent prosecution can abandon an application and file a continuation. Alternatively, a patentee can prosecute one or more patents to issue and also keep a continuation application on file, hoping to win a better patent from the PTO in the future. We describe this rather remarkable practice in Part I. We also report the results of our comprehensive empirical study of continuation applications, which demonstrates the frequency with which this process is used and abused. In an effort to study the pervasiveness of this practice, we compiled an original dataset comprising 2,224,379 patents, every patent issued from 1976 through 2000. We collected the data on the patent filing dates, issuance dates, whether the patent claimed priority to an earlier filed application, the date of the earliest claim to priority, and whether any other patent in the priority chain was issued and when.

Continuation practice has a number of pernicious consequences, which we detail in Part II. First, at a minimum, continuation practice introduces substantial delay and uncertainty into the lives of a patentee’s competitors, who cannot know whether a patent application is pending in most circumstances. Second, the structure of the PTO suggests that continuations may well succeed in “wearing down” the examiner, so that the applicant obtains a broad patent not because he deserves one, but because the examiner has neither incentive nor will to hold out any longer. Third, continuation practice can be-and has been-used strategically to gain advantages over competitors by waiting to see what product the competitor will make, and then drafting patent claims specifically designed to cover that product. Finally, some patentees have used continuation practice to delay the issuance of their patent precisely in order to surprise a mature industry, a process known as “submarine patenting.”

Congress and the courts have created a number of patent doctrines designed to combat the misuse of continuation applications. In the last ten years, they have changed the term of patents, ended the secrecy of most patent applications, revived the controversial doctrine of written description, and created an entirely new defense of prosecution laches. While these changes have indeed mitigated some of the worst abuses of the continuation process, our data demonstrate that they are not likely to be effective in tackling the core of the problem.

One simple solution to the problems that beset continuations would be to abolish the practice. Part III explores this alternative. In it, we consider the various justifications that have been offered for continuation practice and find many of them wanting. We also consider various complicating factors and potential downsides to abolishing continuations. We conclude from our empirical research that, while there are very real abuses of the system attributable to continuation practice, they may not be so widespread as to justify eliminating continuation practice entirely. Whether continuations should be abolished entirely depends on a judgment concerning the benefit continuations provide to applicants who are legitimately trying to draft effective patent claims.

As alternatives to this drastic remedy, we offer a number of other steps that Congress and the courts could take to restrict abuse of continuations. These steps include requiring publication of all applications, placing a time limit on the addition of new claims that broaden the scope of the patent, and creating a defense for infringers who independently developed the patented invention before it was added to the patent claims. At a bare minimum, our data should enable the courts to add some rigor to the new doctrine of prosecution laches by providing a baseline against which to judge the reasonableness of any particular patentee’s delay.