As the formation of government coalitions between two or more political parties is a typical procedure in multiparty systems after elections and the parties’ decision on what coalition to form heavily influences policy outcomes, electorates, academics, and other stakeholders like journalists or party officials increasingly need digital tools that can determine the parties’ most preferred coalitions. This article presents a novel visualization tool for identifying utility-maximizing choices and equilibrium coalitions to provide users with rapid analyzing capabilities revealing parties’ most preferred coalitions in the aftermath of parliamentary elections. We demonstrate our tool’s analytical leverage taking the 2017 German federal elections as in-depth example. Our tool is available online at www.mytuc.org/mcbz .

Mit dieser Dissertationsschrift liegt die erste Studie vor, in der die Aussage- und Erklärungskraft der parteipolitischen Positionierungen aller Wahl-O-Mat-Versionen der Bundes- und Länderebene im Zeitraum 2002 bis 2017 anhand von Parteipositionen aus Referenzverfahren, Modellen formaler Koalitionstheorie sowie Methoden der Computational Social Science untersucht wird. Die Studie behandelt die Leitfrage aus Nutzerperspektive (Wahl-O-Mat als Wahlhilfetool) und aus der Sicht der die Parteipositionen anwendenden Parteienforschung (Wahl-O-Mat als Datenquelle parteipolitischer Positionierungen). Ein Ergebnis der Studie lautet, dass Wahl-O-Mat-Parteipositionen über einen hohen Informationsgehalt zur Erklärung von Koalitionsbildungen verfügen.

This dissertation examines the validity and explanatory power of party positions used by the German application ‘Wahl-O-Mat’, which offers voting advice. The study considers all the Wahl-O-Mat versions provided for the German federal and state elections from 2002 to 2017, refers to validated reference positions and incorporates formal coalition theory. One of the study’s findings is that Wahl-O-Mat-based party positions possess substantial information content that can explain coalition formation.

While prior work on coalition theories focuses either solely on office or on policy motivations of parties, more elaborate theories combine both types of motivation. Said combination makes them much more appropriate for explaining coalition formation but also more complex. One possibility to make these models broadly applicable are coalition tools. Since existing tools do not incorporate advances from such theories, we present a new coalition tool called Coalizer which takes both office and policy motivations into account and reflects the state of coalition theory. Among others, Coalizer includes features like the computation of policy utility values basing on party positions (supporting different estimation modes), the combination of office and policy utility values, and the indication of utility maximizing strategies for parties. In this paper, we present our coalition tool and illustrate its functionality with the example of the German federal elections in 2017. Coalizer is available online at www.mytuc.org/mcbz