Wikipedia as a Data Source for Political Scientists: Accuracy and Completeness of Coverage

In only 10 years, Wikipedia has risen from obscurity to become the dominant information source for an entire generation. However, any visitor can edit any page on Wikipedia, which hardly fosters confidence in its accuracy. In this article, I review thousands of Wikipedia articles about candidates, elections, and office holders to assess both the accuracy and the thoroughness of Wikipedia's coverage. I find that Wikipedia is almost always accurate when a relevant article exists, but errors of omission are extremely frequent. These errors of omission follow a predictable pattern. Wikipedia's political coverage is often very good for recent or prominent topics but is lacking on older or more obscure topics.