Game Theory, Coalition Formation and Political Power Concentration in the Prague City Assembly

The objective of the paper is to study the political development in the Prague City Assembly after three elections in 2006, 2010, and 2014. The theory of voting games, the Shapley-Shubik and Banzhaf power indexes, and theories of coalition formation are used for an analysis of possible majority coalitions. We developed the mayor's power index that measures the probability that the party will be the strongest party in the majority coalition with the right having a mayor. Measures of concentration of political power are used for evaluating the processes of political fragmentation.The increased number of political parties represented in the Prague City Assembly highly increased the number of possible coalitions and the number of political parties needed to form majority coalitions. The process of political fragmentation is probably not limited only to the Prague City Assembly.