Keyword advertising, or sponsored search, is one of the most successful advertising models on the Internet. One distinctive feature of keyword auctions is that they enable advertisers to adjust their bids and rankings dynamically, and the payoffs are realized in real time. We capture this unique...

The literature of private provision of public goods suggests that incentive to contribute is inversely related to group size. This paper empirically tests this relationship using field data from Chinese Wikipedia, an online encyclopedia. We exploit an exogenous reduction in group size as a...

We examined whether people conform to or diverge from the most popular choice among their friends by conducting a large-scale field experiment on a leading social-networking site in China. Our setting allowed us to minimize confounding effects such as pre-existing taste similarities between a...

The literature on the private provision of public goods suggests an inverse relationship between incentives to contribute and group size. We find, however, that after an exogenous reduction of group size at Chinese Wikipedia, the nonblocked contributors decrease their contributions by 42.8...