That is the job market paper from Lei Xu, at McGill University, co-authored with Nian and Cabral at NYU’s Stern School. Here is the abstract:
Many online platforms such as Yahoo! Answers and GitHub rely on users to voluntarily provide content. What motivates users to contribute content for free however is not well understood. In this paper, we use a revealed preference approach to show that career concerns play an important role in user contributions to Stack Overflow, the largest online Q&A community. We investigate how activities that can enhance a user’s reputation vary before and after the user finds a new job. We contrast this with activities that do not help in enhancing a user’s reputation. After finding a new job, users contribute 25% less in reputation-generating activity on Stack Overflow. By contrast, they reduce their non-reputation-generating activity by only 8% after finding a new job. These findings suggest that users contribute to Stack Overflow in part because they perceive this as a way to improve future employment prospects. We provide direct evidence against alternative explanations such as integer constraints, skills mismatch, and dynamic selection effects. The results also suggest that, beyond altruism, career concerns play an important role in explaining voluntary contributions on Stack Overflow.
I think of this as yet another paper on how reputation can (sometimes, not always) enable the private production of public goods.