Legislative effectiveness hangs in the balance: Studying balance and polarization through partitioning signed networks

Over the past several decades in the US Congress, there has been a decline in the fraction of bills introduced that eventually become law. This decline in legislative effectiveness has occurred in parallel with rising levels of political polarization, where coordination occurs primarily within not between groups, which are often defined by political party affiliation. However, in part due to challenges in measuring political polarization, the link between effectiveness and polarization is unclear. In this article, we have two goals. Methodologically, we propose a general method for identifying opposing coalitions in signed networks. Substantively, we use the partisanship of such coalitions in the US Congress since 1979 to examine the impact of polarization on rates of bill passage. Based on the legislative process used by the US Congress, it might be expected that a chamber's bills are more likely to become law when the controlling party holds a larger majority. However, we show that changes in bill passage rates are better explained by the partisanship of a chamber's largest coalition, which we identify by partitioning a signed network of legislators into two mutually opposing, but internally cohesive groups.