Theoretical Computer Science ( IF 1.1 ) Pub Date : 2019-09-11 , DOI: 10.1016/j.tcs.2019.09.015 Marios Mavronicolas , Burkhard Monien
Conditional Value-at-Risk, denoted as , is becoming the prevailing measure of risk over two paramount economic domains: the insurance domain and the financial domain; is the confidence level. In this work, we study the strategic equilibria for an economic system modeled as a game, where risk-averse players seek to minimize the Conditional Value-at-Risk of their costs. Concretely, in a -equilibrium, the mixed strategy of each player is a best-response. We establish two significant properties of at equilibrium: (1) The Optimal-Value property: For any best-response of a player, each mixed strategy in the support gives the same cost to the player. This follows directly from the concavity of in the involved probabilities, which we establish. (2) The Crawford property: For every α, there is a 2-player game with no -equilibrium. The property is established using the Optimal-Value property and a new functional property of , called Weak-Equilibrium-for-, we establish. On top of these properties, we show, as one of our two main results, that deciding the existence of a -equilibrium is strongly -hard even for 2-player games. As our other main result, we show the strong -hardness of deciding the existence of a -equilibrium, over 2-player minimization games, for any valuation with the Optimal-Value and the Crawford properties. This result has a rich potential since we prove that the very significant and broad class of strictly quasiconcave valuations has the Optimal-Value property.
中文翻译:
条件风险值:均衡的结构和复杂性
条件风险值,表示为,已成为两个最重要经济领域的主要风险度量:保险领域和金融领域; 是置信度。在这项工作中,我们研究了一个以博弈为模型的经济系统的战略均衡,在这种均衡中,规避风险的参与者试图将其成本的有条件风险最小化。具体来说,在均衡,每个参与者的混合策略都是最佳响应。我们建立了两个重要的特性在平衡状态下:(1)所述的优化-值属性:对于演奏者的任何最优反应,在支持各混合策略给出相同的成本给玩家。这直接是由于我们确定的相关概率。(2)所述的克劳福德属性:对于每一个α,有一个2人游戏,没有-平衡。该属性是使用Optimal-Value属性和的新功能属性建立的,称为“弱均衡”,我们建立。在这些属性之上,作为两个主要结果之一,我们表明决定是否存在平衡很强 -即使对于2人游戏也很难。作为我们的其他主要结果,我们展示了强大的-确定一个存在的难度 平衡,超过2人参与的最小化游戏,任何估值 具有“最佳价值”和“克劳福德”属性。由于我们证明了非常重要和广泛的一类严格拟凹估值具有“最优价值”属性,因此该结果具有巨大的潜力。