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arXiv 1004.2565cs.GTcs.DS
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市场与预算匹配中的竞争均衡

Competitive Equilibria in Matching Markets with Budgets

Ning Chen, Xiaotie Deng, Arpita Ghosh

摘要:

我们研究了具有不可分割商品和单位需求买家的经典Shapley-Shubik分配模型中的竞争均衡,预算约束:买家可以指定他们愿意为每个项目支付的最高价格,超过这个价格,他们就买不起这个项目。由预算约束引入的这种单一不连续性从根本上改变了平衡的性质:在没有预算约束的分配模型中,竞争平衡总是存在的,并且恰好对应于稳定匹配。在预算方面,竞争性均衡并不总是存在。此外,现在有两个不同的稳定性概念,取决于买方和卖方中的两个或只有一个可以在阻止对中严格受益,这两个概念不再一致,因为不连续性引起的不连续性。我们定义了弱稳定性和强稳定性的分配模型与可转移的效用,并证明了竞争平衡正好对应于强稳定的匹配。我们认为,有效地计算竞争均衡的算法问题,在扩展的分配模型与预算,每个买家指定他的偏好使用效用函数$u_{ij}$,其中$u_{ij}(p_j)$是买方$i$项目$j$的效用时,其价格是$p_j$。我们的主要结果是一个强多项式时间算法,决定是否存在竞争均衡,如果是的话,计算一个最小的,一般类的效用函数$u_{ij}$。这类效用函数包括具有预算约束的标准准线性效用模型,并且此外,允许建模市场,其中,例如,买家仅具有受每个物品的最大支付限制的物品之间的偏好排名,或者买家希望优化投资回报率(ROI)而不是准线性效用并且仅知道物品的相对价值。

英文摘要:

We study competitive equilibria in the classic Shapley-Shubik assignment model with indivisible goods and unit-demand buyers, with budget constraints: buyers can specify a maximum price they are willing to pay for each item, beyond which they cannot afford the item. This single discontinuity introduced by the budget constraint fundamentally changes the properties of equilibria: in the assignment model without budget constraints, a competitive equilibrium always exists, and corresponds exactly to a stable matching. With budgets, a competitive equilibrium need not always exist. In addition, there are now two distinct notions of stability, depending on whether both or only one of the buyer and seller can strictly benefit in a blocking pair, that no longer coincide due to the budget-induced discontinuity. We define weak and strong stability for the assignment model with transferable utilities, and show that competitive equilibria correspond exactly to strongly stable matchings. We consider the algorithmic question of efficiently computing competitive equilibria in an extension of the assignment model with budgets, where each buyer specifies his preferences over items using utility functions $u_{ij}$, where $u_{ij}(p_j)$ is the utility of buyer $i$ for item $j$ when its price is $p_j$. Our main result is a strongly polynomial time algorithm that decides whether or not a competitive equilibrium exists and if yes, computes a minimum one, for a general class of utility functions $u_{ij}$. This class of utility functions includes the standard quasi-linear utility model with a budget constraint, and in addition, allows modeling marketplaces where, for example, buyers only have a preference ranking amongst items subject to a maximum payment limit for each item, or where buyers want to optimize return on investment (ROI) instead of a quasi-linear utility and only know items' relative values.

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