Transparency in Parliamentary Voting

We use a change in the voting procedures of one of the two chambers of the Swiss parliament to explore how transparency affects the voting behavior of its members. Until 2013, the Upper House (Council of States) had voted by a show of hands. While publicly observable at the time of the vote, legislators' decisions could only be verified ex post through the time-consuming screening of online videos. In 2014, halfway through the legislative period, the chamber switched to electronic voting. Since then, the individual votes of legislators have become more transparent and observable as their votes are now recorded electronically and, in some cases, published online.

Our analysis is based on individual voting behavior in all final passage votes during the 2011- 2015 legislative period. In a difference-in-difference framework, the larger chamber, the Lower House (National Council), serves as a control group. Not only have the voting procedures of the Lower House remained unchanged since 2007 but also the legislative texts on which both chambers vote are the same. This unique framework makes it possible to estimate the causal effects of voting procedures on legislators' choices.

Since the voting system reform, members of the Upper House are significantly less likely to deviate from their party line. Our results reflect the increased observability of legislators' votes and the greater conformity pressure exerted by political parties, as easier monitoring enables them to enforce discipline among their members.