Is Wikipedia biased?

A very interesting study about Wikipedia appeared in the recent issue of the American Economic Review (Greenstein and Zhu, 2012). The article tries to establish if Wikipedia is biased in a political sense? Are articles more left or right leaning? The question is interesting because Wikipedia is the prototypical medium built entirely on user-generated content. But Wikipedia is not just a social network where personal information constitutes the overwhelming majority of uploaded content. Wikipedia is an encyclopedia meant to summarize the collective knowledge of mankind.

The article finds that Wikipedia was indeed biased towards the left (Democratic) in the early years. This bias however, comes from the publishing of more left leaning articles and seems to disappear over time. Essentially, the change doesn't come from the revision of existing articles (this effect is marginal) but rather, from the publishing of new articles in the with an opposite slant (Republican).

The result is comforting: collectively we generate valuable and relatively objective information. The 'wisdom of crowds' is supported in this natural experiment. Yet, it is interesting that, individually, we are quite biased and have a strong need to express this. The study also provides great empirical support to the behavioral assumptions of the entire 'media bias' literature. There, the main argument is that media is biased to cater to the preferences of biased individuals who only want to hear information that is consistent with their views. This, in turn explains a hoard of industry dynamics when media outlets are set out to compete with one another. Those studies only assume biased behavior from individuals. The present study however, shows that indeed, individuals do have a need to reaffirm their biases as opposed to seek objectivity. The good news is that, somehow the market seems to correct for this.