László Á. Kóczy

The Coalition Structure Core is Accessible

For each outcome (i.e. a payoff vector augmented with a coalition structure) of a TU-game with a non-empty coalition structure core there exists a finite sequence of successively dominating outcomes that terminates in the coalition structure core. In order to obtain this result a restrictive dominance relation-which we call enforceable dominance-is employed.

The coalition structure core is accessible

For each outcome (i.e. a payoff vector augmented with a coalition structure) of a TU-game with a non-empty coalition structure core there exists a finite sequence of successively dominating outcomes that terminates in the coalition structure core. In order to obtain this result a restrictive dominance relation - which we label outsider independent - is employed.

Sequential coalition formation and the core in the presence of externalities

The sequential coalition formation model of Bloch to solve cooperative games with externalities exhibits some anomalies when related to classical concepts [Bloch, F., 1996. Sequential formation of coalitions in games with externalities and fixed payoff division. Games Econ. Behav. 14, 90-123]. We elaborate on these problems, define a modification of Blochs model and show that its order-independent equilibria coincide with the (pessimistic) recursive core [Koczy, L.A., 2007. A recursive core for partition function form games. Theory Dec. 63, 41-51].

Beyond Lisbon: Demographic trends and voting power in the European Union Council of Ministers

Decision making has become slow in the 27-member European Union and the Treaty of Nice distributed power in a somewhat arbitrary way. The Lisbon Treaty makes decision making easier, and streamlines the process by removing the most controversial element: the voting weights. The new system relies entirely on population data. We look at the immediate impact of the reform as well as the long term effects of the different demographic trends across countries. We find that the Lisbon rules hurt medium sized countries, especially Central Eastern European countries with declining populations, most, while the United Kingdom is the clear winner.

The Core of a Partition Function Game

We consider partition function games and introduce new definitions of the core that include the effects of externalities. We assume that all players behave rationally and that all stable outcomes arising are consistent with the appropriate generalised concept of the core. The result is a recursive definition of the core where residual subgames are considered as games with fewer players and with a partition function that captures the externalities of the deviating coalition. Some properties of the new concepts are discussed.

Fair Apportionment in the View of the Venice Commission's Recommendation

In this paper we analyze the consequences of the fairness recommendation of the Venice Commission in allocating voting districts among larger administrative regions. This recommendation requires the size of any constituency not to differ from the average constituency size by more than a fixed limit. We show that this minimum difference constraint, while attractive per definition, is not compatible with monotonicity and Hare-quota properties, two standard requirements of apportionment rules. We present an algorithm that efficiently finds an allotment such that the differences from the average district size are lexicographically minimized. This apportionment rule is a well-defined allocation mechanism compatible with and derived from the recommendation of the Venice Commission. Finally, we compare this apportionment rule with mainstream mechanisms using real data from Hungary and the United States.

Intellectual Influence: Quality Versus Quantity

To take development and budgeting decisions for research activi- ties the officials in charge need to constantly evaluate and assess the quality of research. Over the years a handful of scoring methods for academic journals have been proposed. Discussing the most prominent methods (de facto standards) we show that they cannot distinguish quality from quantity at article level and that they are inherently biased against journals publishing more articles. If we consider the length of a journal by the number of pages or characters, then all methods are biased against lengthier journals. The systematic bias we nd is analytically tractable and implies that the methods are ma- nipulable. We show that the strategies for successful manipulation are relatively easy to infer and implement. The implications of our ndings extend beyond the evaluation of academic research, to related settings like the ranking of web domains. Non-manipulable methods for measuring intellectual in uence exist.

The invariant method can be manipulated

We show that the invariant method [Pinski & Narin, 1976], recently axiomatised by Palacios-Huerta & Volij [2004], and used to quality-rank academic journals is subject to manipulation: a journal can boost its performance by making additional citations to other journals.

The Core in the Presence of Externalities

We generalise the coalition structure core to games in partition function form. In our definition we make only one assumption, namely that there is some internal consistency in the game: Residuals of the deviation play a game similar to the initial one, and come to a residual core outcome – whenever this is possible. Deviating players form their optimistic or pessimistic expectations with this in mind. This leads to a recursive definition of the core. When compared to existing approaches, our core concept shows a reduced sensitivity to behavioural assumptions. We look at the core of an economy with a common pool resource defined by Funaki and Yamato (1999) and find that for a number of numerical examples our core concept resolves the contradiction, which arose when more naive approaches were used. Possibilities for further extensions are outlined.

The Core in Normal Form Games

Due to the externalities, in normal form games a deviation changes the payoff of all players inducing a retaliation by the remaining or residual players. The stability of an outcome depends on the expectations potential deviators have about this reaction, but so far no satisfactory theory has been provided. The present paper continues the work of Chander and Tulkens (1997) where deviators consider residual equilibria, but we allow coalitions to form, moreover introduce consistency between the residual solution and the solution of the original game. Optimistic and pessimistic considerations produce a pair of cores. These cores are compared to some existing cooperative concepts such as the gamma- and r-cores and the equilibrium binding agreements. In our final section we discuss the predominance of the grand coalition and suggest a generalisation of the normal form where such a precedence can be removed.