Party Voting Unity and Collective Accountability

When votes are visible, what can we learn from them about legislative accountability? Citizens can learn whether specific representatives have pursued their interests in motions put to a vote on the floor – information that can provide a basis for individual legislative accountability. Even apart from the policy substance of the votes themselves, voting patterns can tell us about prospects for collective accountability, because collective accountability requires that groups of legislators vote in a unified manner to shape outcomes on the floor.

I propose various measures of voting unity and success among groups of legislators. Because parties are the ubiquitous organizers of legislative work, the groups on which I focus primarily are parties, so unless otherwise noted, voting unity and related terms refer to unity among members of the same party. The measures of unity, however, can be equally well applied to any other group, such as coalitions that encompass more than one party or legislators from a particular region, sex, race, or religion – any characteristic of interest for analysis.

Why should we care about party unity in legislative voting? First, legislative votes are the means by which major public policy decisions are ratified in all democracies. Voting behavior is of intrinsic interest because the stakes are high. Second, political parties are potentially important information conduits to citizens. Parties can pledge to support comprehensive policy platforms on which individual politicians cannot credibly claim to have much impact.