In recent years, American companies have faced a growing threat from patent assertion entities derisively called "patent trolls." These often shadowy firms make money by threatening patent lawsuits rather than creating useful products. A recent study suggests that the roots of the patent trolling problem may lie with the US Patent and Trademark office—specifically with patent examiners who fail to thoroughly vet patent applications before approving them.

So-called patent trolls "disproportionately purchase and assert patents that were granted by 'lenient' examiners," write Harvard economist Josh Feng and his co-author Xavier Jaravel of the London School of Economics in a December paper.

Patent examiners don't just decide whether or not to approve a patent. They're also supposed to narrow a patent's claims to make sure it only covers what the inventor actually invented. But some examiners do a better job of this than others. Feng and Jaravel found that examiners who demand the fewest changes to patent claims account for a disproportionate share of patents that ultimately wind up in patent lawsuits.

And these effects are large: the pair found that patents reviewed by examiners who are one standard deviation more "lenient" than average are 63 percent more likely to be purchased by a patent enforcement entity and 64 percent more likely to be involved in litigation.

The study reinforces earlier research suggesting that the country's problems with low-quality patents and rampant patent litigation is driven by inadequate scrutiny of patents by patent examiners. It suggests that giving patent examiners better training and more time to scrutinize each patent could improve patent quality and bring down frivolous patent litigation over time.

Examiners are supposed to police patent claims

The heart of any patent is its claims, a numbered list that specifies exactly what technology the patent covers. An important part of the patent examination process is haggling over the exact wording of these claims.

A patent attorney seeking a patent on behalf of a client will typically seek the broadest possible wording, since that makes the patent more powerful. But patent examiners are supposed to push back, asking for clear and specific language—language that only claims what the inventor actually invented, not a broader class of related technologies.

If an examiner is doing a thorough job of vetting patent claims, we would expect the examiner to seek more changes to patent claim language. And most of those changes will involve adding qualifiers to the claim, making it longer. So Feng and Jaravel realized that the change in patent claim length could serve as a proxy for how thoroughly a patent examiner was doing his or her job.

The researchers also looked at how the number of claims in a patent changed between the initial application and the final patent. Often an examiner will approve some claims while ruling that others are too far removed from what the applicant actually invented. This means that more thorough patent examiners are likely to produce a bigger reduction in the number of claims between an initial application and a final patent.

Finally, Feng and Jaravel looked at how many different provisions of patent law examiners cited as grounds for narrowing or rejecting patent claims. Patent law provides a variety of reasons to reject a patent claim, such as obviousness or a lack of novelty. The researchers gathered data on how many different provisions of patent law each examiner invoked, on the theory that a more effective examiner would invoke more patent law provisions, on average.

The pair also gathered data about what happened to patents after they were approved—whether they were acquired by a conventional operating company or by a so-called patent troll and whether they were ultimately used in patent litigation.

The results were striking. For example, the researchers looked at patents from examiners whose average change in patent claim length was one standard deviation below average—suggesting that the claims in these patents had received below-average scrutiny. These patents were 13.9 percent more likely to be involved in litigation if they were owned by a regular firm, and they were 40.5 percent more likely to be involved in litigation if they were owned by the kind of firm that often gets accused of patent trolling.

Josh Feng and Xavier Jaravel

Josh Feng and Xavier Jaravel

Josh Feng and Xavier Jaravel

Josh Feng and Xavier Jaravel

The other measures of examiner leniency showed smaller but still significant effects on the acquisition and use of patents by shadier firms. For example, if an examiner removed one standard-deviation fewer claims from patents than other examiners, her patents were 7.3 percent more likely to be subsequently purchased by patent trolls. Examiners who invoked fewer sections of patent law, on average, produced patents that were more likely to be acquired by patent trolls and used for litigation.

Of course, correlation does not prove causation, and you might worry that these differences reflect examiners being asked to look at different types of patents. But the researchers say they account for this possibility by focusing on comparisons within "art units"—sections of the patent office that focus on a particular category of technology. Some art units assign applications to examiners on an effectively random basis, so two examiners within the same art unit should be getting applications with similar characteristics. The researchers argue that rules out the possibility that the differences are explained by the applications the examiners are receiving rather than the work the examiners are doing.

Should we give patent examiners more time and training?

Back in December, we wrote about research suggesting that patent examiners would be able to do a more thorough job with patent applications if they were given more time. A particular patent examiner's rejection rate tends to go up gradually over time, as he or she gets better at finding valid grounds for rejecting a patent.

However, when an examiner gets a promotion, the pay raise comes with a larger quota, requiring the examiner to spend less time on each application. The result: the examiner's rejection rate suddenly falls, indicating he or she no longer has enough time to do as thorough a job weeding out bad patents.

While those earlier researchers focused on the decision to accept or reject a patent application, Feng and Jaravel focus on ways that patent examiners change a patent before accepting it. And the latter researchers don't have any direct evidence about why some patent examiners seem to do a more thorough job than others.

Still, it seems like a reasonable guess that more time would be helpful. When examiners request changes to a patent's claims, they are supposed to provide a legal basis for the changes. Hence, if examiners were given more time to work on each patent, it's likely patents would get reviewed more thoroughly, leading to more changes that make patent language narrower and clearer. And Feng and Jaravel's research suggests that this would make the resulting patents less attractive to patent trolls and less likely to wind up in litigation more generally.

More training might also help. While some examiners may not have time to do a thorough job, others might not be sufficiently familiar with the full range of legal requirements a patent must satisfy.

Of course, giving examiners more training or more time to do their jobs would cost more money. Michael Frakes—a legal scholar at Duke and the co-author of that earlier study showing how patent examiners approve more patents when they have less time to examine them—says that there's a lively debate among patent law experts about whether it makes sense to give the patent office more money to spend weeding out bad patents.

Frakes points to a famous 2001 paper by patent scholar Mark Lemley, which argued that spending more money weeding out bad patents actually didn't make sense.

"Very few patents are actually litigated or licensed," Lemley argued. "Most simply sit on a shelf unused." So there's an argument in favor of waiting to find out which patents actually matter—and then have the courts litigate whether those patents are actually valid or not.

But Frakes told Ars that argument hasn't aged well. Over the last 17 years, we've seen the rise of patent trolls that exploit the vagueness of patents and the high costs of litigation to extort money out of victims who simply can't afford to vindicate their rights in court. Patent trolling costs the US economy tens of billions of dollars per year. Spending an extra billion weeding out the kind of patents that have fueled the troll boom could be money well spent.