Backlog of unexamined patent applications
Although not clearly defined, the backlog of unexamined patent applications consists, at one point in time, of all the patent applications that have been filed and still remain to be examined. The backlog was said to be 4.2 million worldwide in 2007, and in 2009 it reportedly continued to grow. Alone, the United States Patent and Trademark Office (USPTO) was reported to have, in 2009, a backlog of more than 700,000 patent applications. According to Beth Simone Noveck, According to Alison Brimelow, former president of the European Patent Office, the "backlog of patent applications is  counter-productive to legal certainty, and that has a negative effect on the innovation process". According to a 2010 study by London Economics, "the cost to the global economy of the delay in processing patent applications may be as much as £7.65 billion each year." According to former U.S. federal judge Paul R. Michel, in an interview conducted in 2011, "delay is [...] the greatest problem with the [U.S.] patent system" and "[the USPTO] desperately needs thousands of additional examiners and new IT systems. Indeed, it has needed them for years." Since 2006, a number of collaborations, known as Patent  Prosecution Highway (PPH), have been set up between various patent offices, in order to avoid the duplication of search and examination work and ultimately reducing the patent backlog. Also, several national patent offices, including United States Patent and Trademark Office (USPTO), implemented programs for prioritized examination of patent applications in narrow categories or for patents applied by small firms. Some of these programs have been found to benefit small firms in terms of patent citations and quality; however, possibly because of higher patent quality and thus importance, the patents issued were more likely to be litigated. However, those applying for  patents can sometimes prefer a lengthy 'patent pending' period and the legal uncertainty that it brings.