Information exchange and multiple peer groups: A natural experiment in an online community
利用在线孕产社区中基于预产期形成的默认同伴群体，发现额外加入其他群体反而减少了用户在默认群体和所有群体中的信息交换，但更高级的群体能缓解这种减少。
We utilise a quasi-experimental setup to identify causal effects of having additional peer groups on information exchange in a large online maternity community. The information exchange is a key performance indicator for the community as well as a public good among users. Pregnant users join default peer groups based on estimated due date (EDD). Natural uncertainties of EDD can lead to multiple peer groups. Using EDD as an instrumental variable, we find that additional peer group(s) reduces information exchange in both default peer group and total peer groups. Having more advanced groups mitigates the reduction, likely due to information spillovers.