Current Projections on Seats, Coalitions and Ministry Assignment for the 2017 German Federal Elections
The German federal elections of September 24 are quickly approaching, and as usual there is uncertainty not only on whether poll data are accurately predicting the upcoming election results, but also on what will be the political consequences of a new allocation of seats in the parliament as soon as those results are finalized.
Based on weekly poll data (INSA/YouGov), we predict:
– The number of seats for each party above the 5% cut-off
– All minimal winning coalitions
– All stable coalitions (according to the conditional Shapley value: see A. Casajus and P. La Mura, ‘The Conditional Shapley Value’. HHL Working Papers, 2017.)
– For each stable coalition, the proportion of ministries that each member party would receive.
To start, press Evaluate.
The table at the top of the output window shows the predicted fraction of the total vote for each of those parties according to current poll data, as well as the predicted number of seats to each party. The last column in the table (‘Strength’) shows the bargaining power (as measured by the Shapley value) that each party would enjoy in any coalition talks based on the predicted seats assignment, regardless of ideological propensity or aversion towards other potential coalition partners.
The remaining lines of output list all minimal winning coalitions according to current poll data, and all winning coalitions which are stable with respect to the conditional Shapley value.
One can see from the output that there are 11 minimal winning coalitions, namely, coalitions in which all members are needed in order to achieve a majority. Of those 11 minimal winning coalitions there are four which in addition are also stable with respect to the conditional Shapley value. That means that, if all parties formulate their expectations according to that same notion, there are no expected profitable deviations which could lead the members of a different winning coalition to assemble together. (One normally speaks about stable coalition structures, but in majority games we can simply denote a stable structure by its minimal winning coalition.)
Yet, the four stable coalitions (BCDE, BCDF, BCEF, and BDEF) are all unrealistic in that they would involve parties that are ideologically very different, and moreover would violate explicit campaign promises. If we include all explicit campaign commitments, namely, that no other party would offer its support to a coalition with F, and that party D would not support any coalition with E, then the resulting stable coalitions (according to the conditional Shapley value) are ACD (‘Jamaica’), and ACE.
Press the Evaluate button to see the outcomes in case explicit campaign commitments are taken into account.
The proportion of ministries for a party in a given coalition (‘Power’) is predicted by the Strength of that party times the Stability coefficient of the coalition. Hence, if coalition AB forms, party B would receive 10% of (60/19), which is just above 30% of the ministry positions, while A would receive the remaining 70%. By contrast, if coalition ACD forms party A would receive 13/60 times 60/17, which is just above 75% of ministry positions; party C would receive 1/20 times the same coefficient of 60/17, which is about 18% of ministries; and party D would receive the remaining 7%.
Comparing the current scenario with the situation after the 2013 election, the results can be summarized as follows. Let us stipulate that a Chancellor position is roughly worth five ministries, so that a total of 20 ministerial positions must be assigned to coalition partners.
In 2013, in the absence of the FDP as a potential coalition partner, the CDU/CSU conceded six ministries (about one third of the total) to the SPD in order to form the ‘Grand Coalition’ AB. Today, based on current poll data the SPD would still expect to receive about six ministries (30% of the total) in order to form a Grand Coalition with the CDU/CSU. But now that the FDP is once again above the 5% cut-off, and hence available as a coalition partner, the CDU/CSU can also form coalition ACD while offering a total of about five ministries to its partners, namely, three or four ministries to the Green (18% of the total) and one or two to the FDP (7% of the total).
Press the Evaluate button to see the coalition and ministry assignment predicted by the conditional Shapley value based on the 2013 election results.
Note that, despite the existence of a winning coalition BCE, in which the SPD would have expected one third of the ministerial positions, the SPD decided to accept the same one-third share in a Grand Coalition with the CDU/CSU. This suggests that the decision of the SPD was also motivated by a desire to second, rather than counteract, the large shift of votes to the right that the 2013 election had brought up by positioning itself as member of a centrist, rather than left-wing, coalition. From its side, the CDU/CSU preferred to offer one extra ministry (six rather than five) to the SPD in order to make the AB coalition just as attractive as the alternative BCE would have been from the perspective of its coalition partner, and hence remove any potential threat of being excluded from the government.
Prof. Dr. André Casajus and Prof. Pierfrancesco La Mura, Ph.D.
Chair of Economics and Information Systems
HHL Leipzig Graduate School of Management