Revealing the Anatomy of Vote Trading

TL;DR

This paper introduces a scalable method to detect vote trading networks, revealing patterns of logrolling in the U.S. Congress over 40 years and showing its decline amid increasing polarization.

Contribution

A novel, general methodology for uncovering vote trading networks that can be applied broadly to study hidden cooperation in legislative processes.

Findings

Higher prevalence of logrolling in the Senate

Decreasing trend of logrolling over recent congresses

Correlation between polarization and reduced vote trading

Abstract

Cooperation in the form of vote trading, also known as logrolling, is central for law-making processes, shaping the development of democratic societies. Empirical evidence of logrolling is scarce and limited to highly specific situations because existing methods are not easily applicable to broader contexts. We have developed a general and scalable methodology for revealing a network of vote traders, allowing us to measure logrolling on a large scale. Analysis on more than 9 million votes spanning 40 years in the U.S. Congress reveals a higher logrolling prevalence in the Senate and an overall decreasing trend over recent congresses, coincidental with high levels of political polarization. Our method is applicable in multiple contexts, shedding light on many aspects of logrolling and opening new doors in the study of hidden cooperation.