No agreed-upon definition of patent troll exists. The term patent troll is used interchangeably with the terms non-practicing entities (NPEs) and patent assertion entities (PAEs). Despite similar sounding names, several key differences exist between the three terms.
'''Non-practicing entities(NPEs)''' own patents, but do not necessarily create products out of these patents. This behavior is common; 95% of patents are never used commercially [http://www.wired.com/2015/01/fixing-broken-patent-system/]. Universities are examples of non-practicing entities. Faculty members may file for patents based on their work in a laboratory and receive a patent. Then, those faculty move on to a different project and do not use the patent they hold.
'''Patent assertion entities (PAEs)''' are a type of non-practicing entity that generate a majority of their revenue through licensing patents they own. For example, a large firm may buy up a thousand patents. Instead of creating products derived from those patents, they license these patents to other firms that wish to create those products. If another firm infringes on a patent, the patent-assertion entity may send a demand letter to the company with a warning. The demand letter warns the infringer that they are subject to a lawsuit if they do not acquire proper licensing of a patent.
In illiquid markets where asets cannot be sold or exchanged easily, patent assertion entities can help match patent holders to patent buyers and transfer ideas and technology from inventors to manufacturers effectively. This allows inventors to focus on innovation while benefiting from the knowledge and connections that intermediaries possess. Patent assertion entities are able to incentivize innovation through the effective brokerage of patents. [https://www.whitehouse.gov/sites/default/files/docs/patent_report.pdf] They manage risks for small inventors and inform manufacturers or inventors of the usefulness of having another inventor's patent in their patent portfolio. [http://www.bna.com/challenges-of-defining-a-patent-troll/]
According to the U.S. Census Bureau, small businesses with less fewer than 20 employees made up 89.6 percent of employer firms in the United States in 2012. [http://sbecouncil.org/about-us/facts-and-data/] Small firms produce more patents per employee than large companies and help drive innovation in the United States economy. The patents they develop have a greater impact and are often more technologically important than those of large firms. [http://www.imamidejo.si/resources/files/doc/analiza%20patentov%20v%20msp%20usa.pdf] The Small Business Administration reported that "although small firms account for only 8 percent of patents granted, they account for 24 percent of the patents in the top 100 emerging clusters." [http://sbecouncil.org/about-us/facts-and-data/] Because small businesses and emerging companies are not always able to protect their patents on their own and account for much of the innovation driving emerging industries today, they need patent assertion entities who have the power to protect their patents for them.
=An Illustration of Patent Troll Activity=