Simulating Intergovernmental Negotiations with MAS

Nicole Saam

University of Marburg, Ketzerbach 11, D-35032 Marburg, Germany

Why do international negotiations fail or succeed? The success story of the constitutionalization of the European Union seems to be seriously challenged since december 2003 when the head of member states admittedly failed to decide on a proposal on it's future constitution. Media ventilated the reason to be the obstinate refusal of Poland and Spain to accept a new reweighting of votes. This reweighting would have abolished a compromise of the conference in Nice in 2000. Obviously, previously applied technics of compromising during long negotiations were not successful - or even attempted. However, the public impression of one-shot intergovernmental conference negotiations and the invoking of a single cause of failure are inconclusive. Such negotiations span months of formal meetings and informal coordination between member states. Furthermore, they are not separated from ongoing political business and events - at the international as well as at the domestic level. Therefore, an understanding of negotiation outcomes has to take account of the specific form of the underlying processes and its connectedness to process-relevant determinants. Unfortunately, our knowledge about processes and dynamics of negotiations is scant. Whereas the sophistication of game-theoretic models has increased enormously during the last decade, their model setup remain highly stylized. The identfication of necessary assumptions for a sequential two-player game immediately ending in a unique equilibrium is ingenious and instructive. However, it does not answer our question. Even if there is a convergence of real world negotiations towards the non-cooperative result of the Rubinstein model or the cooperative Nash-bargaining solution, we would like to know the actors' microbehavior in getting these macro-results. In this lecture, I contribute to a 'comparative game dynamics' (Richard 2000). I present the Zeuthen-Harsanyi model of concession behavior - a predecessor to the Rubinstein model - as a framework for simulating the dynamics of a multilateral, multiple issue, multi-stage and multi-level negotiation system, the EU Intergovernmental Conference of 1996 which led to the Amsterdam treaty. In this model, the 15 EU member states are represented as more or less homogeneous agents who have preferences with respect to 46 issues which are negotiated in parallel processes. The states avoid n-person games in order to economize on transaction costs. Instead, after signaling their preferences, they form coalitions. The negotiations are reconceptualized as Zeuthen-Harsanyi model for two coalitions. In order to evaluate the appropriateness of the simulation model several goodness of fit parameters are calculated. These parameters are based on different kinds of predicted outcome (simulated or regressed) as well as the empirical outcome - the Amsterdam treaty - which has been operationalized (cf. Thurner/Pappi/Stoiber 2002).