Dynamic weighted voting games.

We initiate the study of dynamic cooperative games --- cooperative games where the characteristic function may change over time. We introduce two types of algorithmic problems for such games: computing a given solution concept at time t, and checking that a certain function of the game (e.g., the Shapley value of a given player or the value of the least core) remains within given bounds during time interval [t_0, t_1]. We then investigate the complexity of these problems for dynamic weighted voting games, where the weight of each player and the quota are functions of time that are given by low-degree polynomials with integer coefficients. We provide pseudopolynomial algorithms for problems of both types, for a variety of solution concepts. We then use our results to investigate the changes in power distribution in the Council of the European Union over the next 50 years.