Power index research
CCST
Weighted power index
Measuring the power of parliamentary groups in the German Bundestag and in the German state parliaments
Traditional power index research is only helpful in measuring the power of parliamentary groups to a limited extent. After all, the Banzhaf, Shapley-Shubik or Penrose indices do not take into account the substantial or ideological proximity of parliamentary groups to each other when measuring power. However, in addition to its size, the position of a party in the party structure, i.e. its substantial or ideological positioning, obviously has a significant influence on its ability to influence the formation of a government or individual voting results in parliament, in short: its power.
But how can the power of a parliamentary group - relative to the power of the other parliamentary groups - be measured in a parliament? In 2017, Prof. Dr. Jakob Lempp (CCST) and Prof. Dr. Thomas Pitz developed a weighted power index with cohesion coefficients to measure the relative power of parliamentary groups in parliaments. The substantial proximity of the parliamentary groups can be measured, for example, through assessments by experts, surveys of party supporters or by overlapping the parties' answers to the “Wahl-O-Mat” questions regularly published before elections. In the following, the respective power distributions of the parliamentary groups are clearly presented and analysed following important elections in Germany at state, federal and European level.
The discussion paper on the weighted power index developed in 2017 to measure parliamentary party power can also be accessed in the download section.