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In May 2016, the Chinese question-and-answer platform Zhihu launched Zhihu Live, allowing contributors to hold live talks and collect entrance fees from participants. While contributing to the knowledge available on the platform, how did this new payment-based approach affect users’ unpaid-for contributions? Using evidence generated by this “natural experiment,” HKUST’s Jing Wang and Kai-Lung Hui and a co-researcher found that the paid feature promoted free contributions without negatively affecting contribution quality.

“Consumers benefit from both paid and nonpaid knowledge,” the authors write. If the “spillover effect” of a financial incentive is a reduction in the quantity or quality of free content, the community’s overall utility will also decline. However, if the option of payment prompts users to write more articles and answer more questions for free, “then its benefit to knowledge contribution is unambiguously positive.” To the best of the authors’ knowledge, this paper is the first “to investigate such spillover effects in both the short and long term.”

Zhihu, with more than 370 million registered users as of December 2020, allows members to ask and answer questions, post essays, comment, and vote on submissions. All contributions made since Zhihu launched in 2011 are freely accessible, thus providing data on members’ behavior both pre- and post-Zhihu Live. By May 2018, Zhihu Live had hosted about 6,000 talks with 7 million paying customers. While the platform does not make recommendations, it does push news of a talk to potentially interested users based on past interactions such as upvoting a speaker’s answers or articles. Making free contributions allows speakers “to raise their visibility and cultivate more potential listeners,” the authors write.

The researchers looked at the two years from the introduction of Zhihu Live in 2016 through 2018, plus the period prior to the launch. Their sample consisted of all 2,240 hosts of at least one Zhihu Live talk in the period, as well as 4,467 non-hosts. Hosts’ contributions to the platform before and after their talks was analyzed and the non-hosts were used to construct matched samples as a comparison.

The researchers found that “the paid feature motivates live hosts to contribute more to the unpaid activity of answering questions in the short term,” with the quality of the answers unchanged. Moreover, because “consumers must pay before accessing the compensated knowledge,” the authors tell us, “contributors need to build a reputation before they can attract a paying audience.” Free contribution “is instrumental to reputation building in an online setting” and increases both the entrance fee that speakers can command and audience size.

Even so, at the platform level, non-hosts’ monthly contributions declined by 32.8% in the study period, while the corresponding drop for live hosts was 18.3%. “It seems that although the answer contribution of users on Zhihu followed a downward trend in our study period,” the authors explain, “the introduction of the live feature has alleviated this reduction by motivating hosts to contribute more free answers.”