Wikipedia has been studied extensively. Between 2001 and 2010, researchers published at least 1,746 peer-reviewed articles about the online encyclopedia. Such studies are greatly facilitated by the fact that Wikipedia's database can be downloaded without help from the site owner.
Research topics have included the reliability of the encyclopedia and various forms of systemic bias; social aspects of the Wikipedia community (including administration, policy, and demographics); the encyclopedia as a dataset for machine learning; and whether Wikipedia trends might predict or influence human behaviour.
Notable findings include factual accuracy similar to other encyclopedias, the presence of cultural and gender bias as well as gaps in coverage of the Global South; that a tiny minority of editors produce the majority of content; various models for understanding online conflict; and limited correlation between Wikipedia trends and various phenomena such as stock market movements or electoral results.
Content
Production
A minority of editors produce the majority of persistent content
Studies from 2005 to 2007 found that a small minority of editors produce most of the edits on Wikipedia, and that the distribution of edits follows a power law with about half of the total edits produced by 1% of the editors. Another 2007 study found that 'elite' editors with many edits produced 30% of the content changes, measured in number of words. These editors were also more likely to add, rather than delete, content.
A 2007 study from the University of Minnesota used reader-based measures that weighted content based on the number of times it was viewed (a persistent word view (PWV)). This study analyzed trillions of word views between September 2002 and October 2006 and concluded that 0.1% of the Wikipedia community (4,200 editors) produced 44% of the word views during this time. The editors concluded that,
A 2009 study determined that one percent of editors who average more than 1,000 edits/month make 55% of edits.
Work distribution and social strata
A peer-reviewed paper noted the "social stratification in the Wikipedia society" due to the "admins class". The paper suggested that such stratification could be beneficial in some respects but recognized a "clear subsequent shift in power among levels of stratification" due to the "status and power differentials" between administrators and other editors.
Analyzing the entire edit history of English Wikipedia up to July 2006, the same study determined that the influence of administrator edits on contents has steadily diminished since 2003, when administrators performed roughly 50% of total edits, to 2006 when only 10% of the edits were performed by administrators. This happened despite the fact that the average number of edits per administrator had increased more than fivefold during the same period. This phenomenon was labeled the "rise of the crowd" by the authors of the paper. An analysis that used as metric the number of words edited instead of the number of edit actions showed a similar pattern. Because the admin class is somewhat arbitrary with respect to the number of edits, the study also considered a breakdown of users in categories based on the number of edits performed. The results for "elite users", i.e. users with more than 10,000 edits, were somewhat in line with those obtained for administrators, except that "the number of words changed by elite users has kept up with the changes made by novice users, even though the number of edits made by novice users has grown proportionally faster". The study concludes:
Reliability
An Argumentation conference paper (2010) assessed whether trust in Wikipedia is based on epistemic or pragmatic merits. While readers may not assess the actual knowledge and expertise of the authors of a given article, they may assess the contributors' passion for the project, and communicative design through which that passion is made manifest, and provide a reason for trust.Goodwin, Jean. (2010). The authority of Wikipedia . In Juho Ritola (Ed.), Argument cultures: Proceedings of the Ontario Society for the Study of Argumentation Conference. Windsor, ON, Canada: Ontario Society for the Study of Argumentation.CD-ROM.24 pp.
In details, the author argued that Wikipedia cannot be trusted based on individual expertise, collective knowledge, or past experience of reliability. This is because anonymity and pseudonymity prevent knowledge assessment, and "anti-expert culture" makes it unlikely that this will change. Editing Wikipedia may largely be confined to an elite group of editors, without aggregating "wisdom of the crowd" which in some cases lowers the quality of an article anyway. Personal experiences and empirical studies, confirmed by incidents including Seigenthaler biography controversy, point to the conclusion that Wikipedia is not generally reliable. Hence, these epistemic factors do not justify consulting with Wikipedia.
The author then proposed rationale to trust Wikipedia based on pragmatic values, which roughly can be summarized into two factors. First, the size and activity around Wikipedia indicates that editors are deeply committed to provide the world with knowledge. Second, transparent developments of policies, practices, institutions, and technologies in addition to conspicuous massive efforts, address the possible concerns that one might have in trusting Wikipedia. The concerns raised include the definition of provided knowledge, preventing distorted contributions from people not sharing the same commitment, correcting editing damages, and article quality control and improvement.
Health information
Health information on English Wikipedia is popularly accessed as results from search engines and search engine result page, which frequently deliver links to Wikipedia articles. Independent assessments of the quality of health information provided on Wikipedia and of who is accessing the information have been undertaken. The number and demographics of people who seek health information on Wikipedia, the scope of health information on Wikipedia, and the quality of the information on Wikipedia have been studied. There are drawbacks to using Wikipedia as a source of health information.
Bias A 2010 study has shown that the average contributor to the English Wikipedia is an educated, technically inclined white male, aged 15–49, from a developed, predominantly Christian country. The corresponding point of view (POV) is over-represented. This systemic bias in editor demographic results in cultural bias, gender bias, and lack of information about the Global South.
There are two broad types of bias, which are implicit (when a topic is omitted) and explicit (when a certain POV is supported in an article or by references).
Interdisciplinary scholarly assessments of Wikipedia articles have found that while articles are typically accurate and free of misinformation, they are also typically incomplete and fail to present all perspectives with a neutral point of view.
Researchers from Washington University in St. Louis developed a statistical model to measure systematic bias in the behavior of Wikipedia's users regarding controversial topics. The authors focused on behavioral changes of the encyclopedia's administrators after assuming the post, writing that systematic bias occurred after the fact.
Geographical bias
Research conducted in 2009 by the Oxford Internet Institute showed that geotagged articles in all language editions of Wikipedia covered about half a million places on Earth. However, the geographic distribution of articles was highly uneven: most articles are written about North America, Europe, and East Asia, with very little coverage of large parts of the developing world, including most of Africa.
Another 2009 study of 15 language editions determined that each edition was highly "self-focused", with emphasis on the geographic "home region" of that language.
Gender bias
The gender bias on Wikipedia has been widely discussed. A 2010 survey found that only 13% of editors and 31% of readers were female. A 2017 paper confirmed that only 15% of the editing community is female.
A 2021 study by Francesca Tripodi found that of the roughly 1.5 million biographical articles on the English Wikipedia in 2021, only 19% were about women. The study found that biographies that do exist are considerably more likely to be nominated for deletion than existing articles of men.
Addressing bias Some studies have investigated the work of WikiProject Countering Systemic Bias (WP:CSB), which is a collective effort of some Wikipedia editors to broaden the encyclopedia's POV. A 2010 study of 329 editors participating in WP:CSB found that these editors' work favoured topics belonging to the United States and England, and that "the areas of the globe of main concern to WP:CSB proved to be much less represented by the coalition itself."
A 2021 paper recommended addressing a "sweet spot" within the encyclopedia's bias where existing scholarship includes reliable, peer-reviewed sources that offer a more complete POV than existing Wikipedia articles. The study suggested that incorporation of these sources would offer better representation for excluded or marginalized POVs, and that the possibilities for potential improvement are "massive."
Natural language processing The textual content and the structured hierarchy of Wikipedia has become an important knowledge source for researchers in natural language processing and artificial intelligence. In 2007 researchers at Technion – Israel Institute of Technology developed a technique called Explicit Semantic Analysis which uses the world knowledge contained in English Wikipedia articles. Conceptual representations of words and texts are created automatically and used to compute the similarity between words and between texts.
Researchers at Ubiquitous Knowledge Processing Lab use the linguistic and world knowledge encoded in Wikipedia and Wiktionary to automatically create linguistic knowledge bases which are similar to expert-built resources like WordNet. Strube and Ponzetto created an algorithm to identify relationships among words by traversing English Wikipedia via its categorization scheme, and concluded that Wikipedia had created "a taxonomy able to compete with WordNet on linguistic processing tasks".
Social aspects
Conflict A 2011 study reported a new way to measure how disputed a Wikipedia article is, and verified against 6 Indo-European language editions including English.
A 2013 article in Physical Review Letters reported a generic social dynamics model in a collaborative environment involving opinions, conflicts, and consensus, with a specific analogue to Wikipedia: "a peaceful article can suddenly become controversial when more people get involved in its editing." cited
In 2014 published as a book chapter titled "The Most Controversial Topics in Wikipedia: A Multilingual and Geographical Analysis": analysed the volume of editing of articles in various language versions of Wikipedia in order to establish the most controversial topics in different languages and groups of languages. For the English version, the top three most controversial articles were George W. Bush, Anarchism and Muhammad. Topics in other languages causing most controversy were Croatia (German), Ségolène Royal (French), Chile (Spanish) and Homosexuality (Czech).
Demographics A 2007 study by Hitwise, reproduced in Time magazine, found that visitors to Wikipedia are almost equally split 50/50 male/female, but that 60% of edits are made by male editors. A 2010 survey found that only 13% of editors and 31% of readers were female. 2017 paper confirmed that only 15% of the editing community is female.