Do Birds of a Feather Vote Together, or Is It Peer Influence?

Why and when do legislators vote together on policy? Do legislators decide to vote similarly mainly because of social influence or similarity? I contribute to the literature by offering a social network theory of voting. It is argued that close social ties help to establish reputations and to aid the flow of information among peer legislators, leading to increased influence and increased rates of co-voting among them. I examine the relative effects of information exchange networks and social exchange networks on rates of co-voting, controlling for similarities among legislators. The data include legislative votes from 2010 to 2014 in the Brazilian Chamber of Deputies. The results suggest that social influence stemming from social relationships exert substantial effects on rates of congressional co-voting.