How Brazilian Congressmen Connect: Homophily and Cohesion in Voting and Donation Networks

Two fundamental activities in the career of a congressman are raising campaign funds and voting on bills. Characterizing the interplay between these two activities is crucial for democracy as it provides explicit feedback to voters on potential conflicts of interest. In this work, we investigate the Brazilian Congress to shed light on the relationships between the donations received by congressmen elected in 2014 and their voting behaviours during 2015 and 2016. By consolidating publicly available data from the House of Representatives and the Superior Electoral Court (TSE), we construct a dataset containing elected congressmen, campaign donors and donations, and legal bills and votes. This leads to the donation network (edges represent co-donation) and voting network (edges represent co-voting) in which nodes are congressmen. We examine homophily and cohesion of congressmen in these two networks with respect to their political parties and electoral regions. Our results indicate that regions exhibit stronger homophily than political parties in the donation network, while this trend is opposite for the voting network. In this sense, we find that partisan cohesion is strong and diverse in the voting network, while regional cohesion is consistently negligible. These findings are an indication of Brazil’s fragmented and weak federalist system where partisan interests override regional interests.