University of Southern California

In World of Wikipedia, Researchers Find Free Ride Not a Concern
Professors Show Link Between Community Size and Contributor Incentives
March 25, 2010 • by News at Marshall

Feng Zhu is passionate about technology strategy. It's both fascinating and exciting, the USC Marshall assistant professor of management and organization says, because "many business models around the technology sector are really new compared to other industries." And, he says, the potential for impact is huge: Successful companies such as YouTube, Facebook and Wikipedia have "an extraordinary opportunity to form a social structure that attracts a phenomenal number of visitors."

Zhu and his co-author, Michael Zhang of HKUST Business School, explore that social structure in "Group Size and Incentives to Contribute: A Natural Experiment at Chinese Wikipedia," a paper forthcoming in the American Economic Review. The paper, says Zhu, set out to address a pressing question: What drives user contributions to online platforms like Wikipedia? "It's a question of incentives," he says. "According to the free-rider hypothesis first proposed by Mancur Olson in 1965, if the platform is small, you may feel like your contribution makes a difference, which might make you more likely to contribute."

Conversely, he says, if the size of the community is extremely large, potential contributors might hold back and we may expect an inverse relationship between group size and incentives to contribute. "For example, if I go to Wikipedia and see a typo, I know there are thousands of other people seeing it, too," he points out. "I might decide not to fix it because I assume someone else will."

Problem solved? It turns out not to be quite so simple. Wikipedia is a community in which users interact with each other, notes Zhu, and "contributors may derive utility from interacting with other contributors and also feel stronger sense of meaningfulness of their contribution from a broader audience." If reaping these social benefits is what motivates contributors, he says, than it would follow that Wikipedia's growth would actually increase their incentive to participate. Put simply, the question boils down to this: Are contributors more or less likely to contribute as group size increases?

As documented in their study of Chinese Wikipedia, the answer is startlingly clear. The Chinese government blocked Wikipedia and as a result of the block, mainland Chinese could not access or contribute to Chinese Wikipedia and the community of contributors shrunk by around 40% - and, says, Zhu, "We find that on average contributors outside mainland China decreased their contribution levels by more than 40% after this reduction in group size."

The two researchers' interpretation: "Contributors really care about the social benefits. And with the block, the shrinking group size weakens these social benefits. Our study suggests that the importance of social benefits ultimately dominates the free-riding incentives." In other words, people decide to contribute less when the community is smaller, because they feel the meaning of their contribution has decreased substantially.

Zhu's joint work has broad implications for practitioners and researchers alike. As the first study looking explicitly at group size and people's contribution levels with more than 1,000 contributors, he says, "It helps explain why many public goods with a large number of contributors can exist in the economy and suggests that future research on these online communities should place more emphasis on social effects than free-riding incentives."

Knowledge gleaned during the study also has real-world applications, says Zhu. "Wikipedia is produced with a collaborative effort, and there are very good social ties among these contributors. Strengthening these social ties even further can help encourage their contributions so they’re more reluctant to leave the community."

In addition, he says, if they know their articles are being read frequently and that readers are benefiting as a result, they presumably will continue to contribute. Therefore, he observes, "these social network platforms can increase contribution levels simply by increasing interactions among community members."

For social networks seeking market share, it comes down to strategy – which, for long-time strategist Zhu, comes as no surprise at all.

To read more about this research:

Zhang, Xiaoquan (Michael) and Zhu, Feng, Group Size and Incentives to Contribute: A Natural Experiment at Chinese Wikipedia. Available at SSRN:

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