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Stability in Matching Markets with Complex Constraints 具有复杂约束的匹配市场的稳定性
Pub Date : 2019-06-17 DOI: 10.1145/3328526.3329639
Thành Nguyen, Hai Nguyen, A. Teytelboym
We consider a new model of many-to-one matching markets in which agents with multi-unit demand aim to maximize a cardinal linear objective subject to multidimensional knapsack constraints. The choice functions of agents with multi-unit demand are therefore not substitutable. As a result, pairwise stable matchings may not exist and, even when they do, may be highly inefficient. We provide an algorithm that finds a group-stable matching that approximately satisfies all the multidimensional knapsack constraints. The degree of the constraint violation is proportional to the sparsity of the constraint matrix. The algorithm therefore provides practical error bounds for applications in several contexts, such as refugee resettlement, matching of children to daycare centers, and meeting diversity requirements in colleges. A novel ingredient in our algorithm is a combination of matching with contracts and Scarf's Lemma.
我们考虑了一个新的多对一匹配市场模型,在该模型中,具有多单位需求的智能体的目标是在多维背包约束下最大化一个基本线性目标。因此,具有多单位需求的主体的选择函数是不可替代的。因此,成对稳定匹配可能不存在,即使存在,也可能效率极低。我们提供了一种算法来寻找一个近似满足所有多维背包约束的群稳定匹配。约束违反的程度与约束矩阵的稀疏度成正比。因此,该算法为一些情况下的应用提供了实际的误差范围,例如难民安置,儿童与日托中心的匹配,以及满足大学的多样性要求。我们的算法中一个新颖的成分是契约匹配和斯卡夫引理的结合。
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引用次数: 22
How to Sell a Dataset? Pricing Policies for Data Monetization 如何销售数据集?数据货币化的定价政策
Pub Date : 2019-06-17 DOI: 10.2139/ssrn.3333296
Sameer Mehta, Milind Dawande, G. Janakiraman, V. Mookerjee
The wide variety of pricing policies used in practice by data-sellers suggests that there are significant challenges in pricing datasets. The selling of a dataset -- arranged in a row-column format, where rows represent records and columns represent attributes of the records -- is more nuanced than that of information goods like telephone minutes and bandwidth, in the sense that, for a buyer, it is not only the amount of data that matters but also the type of the data. We develop a utility framework that is appropriate for data-buyers and the corresponding pricing of the data by the data-seller. A buyer interested in purchasing a dataset has private valuations in two aspects -- her ideal record that she values the most, and the rate at which her valuation for the records in the dataset decays as they differ from her ideal record. The seller allows individual (and heterogeneous) buyers to filter the dataset and select the records that are of interest to them. The multi-dimensional private information of the buyers coupled with the endogenous selection of records makes the seller's problem of optimally pricing the dataset a challenging one. We formulate a tractable model and successfully exploit its special structure to examine it both analytically and numerically. A key result we establish is that, under reasonable assumptions, a price-quantity schedule is an optimal data-selling mechanism. Such a schedule has a nuanced interpretation in the data-selling context in that buyers buy different sets of records but the price for a given number of records does not depend on the identity of the records chosen by the buyer. Even when the assumptions leading to the optimality of a price-quantity schedule do not hold, we show that the optimal price-quantity schedule offers an attractive worst-case performance guarantee relative to an optimal mechanism. Further, we numerically solve for the optimal mechanism and show that the actual performance of two simple and well-known price-quantity schedules -- two-part pricing and two-block pricing -- is near-optimal. We also quantify the value to the seller from allowing buyers to filter the dataset.
数据销售者在实践中使用的各种各样的定价政策表明,定价数据集存在重大挑战。数据集的销售——以行-列格式排列,行代表记录,列代表记录的属性——比电话分钟和带宽等信息商品的销售更微妙,因为对买家来说,重要的不仅是数据的数量,还有数据的类型。我们开发了一个实用程序框架,它适用于数据购买者和数据销售者对数据的相应定价。对购买数据集感兴趣的买家有两个方面的私人估值——她最看重的理想记录,以及她对数据集中记录的估值因与她的理想记录不同而衰减的速度。卖方允许单个(和异构)买家过滤数据集并选择他们感兴趣的记录。买方的多维私有信息与记录的内生选择相结合,使得卖方对数据集的最优定价问题具有挑战性。我们建立了一个可处理的模型,并成功地利用其特殊的结构对其进行了分析和数值检验。我们建立的一个关键结论是,在合理的假设下,价格-数量计划是最优的数据销售机制。这样的时间表在数据销售上下文中有微妙的解释,因为买家购买不同的记录集,但是给定数量记录的价格并不取决于买家选择的记录的身份。即使导致价格-数量计划最优性的假设不成立,我们也证明了最优价格-数量计划相对于最优机制提供了一个有吸引力的最坏情况性能保证。此外,我们对最优机制进行了数值求解,并表明两种简单且众所周知的价格-数量计划(两部分定价和两块定价)的实际性能接近最优。我们还通过允许买家过滤数据集来量化对卖家的价值。
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引用次数: 33
Cloud Pricing: The Spot Market Strikes Back 云定价:现货市场的反击
Pub Date : 2019-06-17 DOI: 10.2139/ssrn.3383420
Ludwig Dierks, Sven Seuken
Cloud computing providers must constantly hold many idle compute instances available (e.g., for maintenance, or for users with long-term contracts). A natural idea to increase the provider's profit is to sell these idle instances on a spot market where users can be preempted. However, this ignores the possible "market cannibalization'' that may occur in equilibrium. In particular, users who would generate more profit in the provider's existing fixed-price market might move to the spot market and generate less profit. In this paper, we model the provider's profit optimization problem using queuing theory and game theory and analyze the equilibria of the resulting queuing system. Our main result is an easy-to-check condition under which offering a market consisting of fixed-price instances as well as some spot instances (using idle resources) increases the provider's profit over offering only fixed-price instances. Furthermore, we show that under our condition, such a profit increase can always be combined with a Pareto improvement for the users. Finally, we illustrate our results numerically to demonstrate the effects the provider's costs and her strategy have on her profit. Full paper: https://ssrn.com/abstract=3383420
云计算提供商必须不断保持许多空闲的计算实例可用(例如,用于维护,或用于有长期合同的用户)。为了增加提供商的利润,一个自然的想法是在现货市场上出售这些闲置的实例,在那里用户可以被抢占。然而,这忽略了均衡状态下可能发生的“市场蚕食”。特别是,在供应商现有的固定价格市场中产生更多利润的用户可能会转移到现货市场,从而产生更少的利润。本文利用排队论和博弈论对供应商的利润优化问题进行了建模,并分析了由此产生的排队系统的均衡问题。我们的主要结果是一个易于检查的条件,在这个条件下,提供一个由固定价格实例和一些现货实例(使用空闲资源)组成的市场比只提供固定价格实例增加了提供商的利润。进一步,我们证明了在我们的条件下,这样的利润增长总是可以与用户的帕累托改进相结合。最后,我们用数字来说明我们的结果,以证明供应商的成本和她的策略对她的利润的影响。全文:https://ssrn.com/abstract=3383420
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引用次数: 39
Managing Market Mechanism Transitions: A Randomized Trial of Decentralized Pricing Versus Platform Control 管理市场机制转变:分散定价与平台控制的随机试验
Pub Date : 2019-06-17 DOI: 10.1145/3328526.3329654
Apostolos Filippas, Srikanth Jagabathula, A. Sundararajan
We report on a randomized trial conducted during a market design transition on a sharing economy platform, where providers who formerly set rental prices for their assets were randomly assigned to groups with varying levels of pricing control. Even when faced with the prospect of significantly higher revenues, providers retaliate against the centralization of pricing by exiting the platform, reducing asset availability and cancelling transactions. Allowing providers to retain partial control lowers retaliation substantially even though providers do not frequently utilize this additional flexibility. We discuss information asymmetry, divergent incentives, and psychological contract violation as alternative explanations for our results.
我们报告了在共享经济平台的市场设计转型期间进行的一项随机试验,其中以前为其资产设定租金价格的供应商被随机分配到具有不同价格控制水平的组。即使面临着显著提高收入的前景,供应商也会通过退出平台、减少资产可用性和取消交易来报复定价的集中化。允许提供商保留部分控制权大大降低了报复,即使提供商并不经常利用这种额外的灵活性。我们讨论了信息不对称,不同的激励和心理契约违反作为我们的结果的替代解释。
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引用次数: 2
The Complexity of Black-Box Mechanism Design with Priors 具有先验的黑盒机构设计的复杂性
Pub Date : 2019-06-17 DOI: 10.1145/3328526.3329648
Evangelia Gergatsouli, Brendan Lucier, Christos Tzamos
We study black-box reductions from mechanism design to algorithm design for welfare maximization in settings of incomplete information. Given oracle access to an algorithm for an underlying optimization problem, the goal is to simulate an incentive compatible mechanism. The mechanism will be evaluated on its expected welfare, relative to the algorithm provided, and its complexity is measured by the time (and queries) needed to simulate the mechanism on any input. While it is known that black-box reductions are not possible in many prior-free settings, settings with priors appear more promising: there are known reductions for Bayesian incentive compatible (BIC) mechanism design for general classes of welfare maximization problems. This dichotomy begs the question: which mechanism design problems admit black-box reductions, and which do not? Our main result is that black-box mechanism design is impossible under two of the simplest settings not captured by known positive results. First, for the problem of allocating n goods to a single buyer whose valuation is additive and independent across the goods, subject to a downward-closed constraint on feasible allocations, we show that there is no polytime (in n) BIC black-box reduction for expected welfare maximization. Second, for the setting of multiple single-parameter agents---where polytime BIC reductions are known---we show that no polytime reductions exist when the incentive requirement is tightened to Max-In-Distributional-Range. In each case, we show that achieving a sub-polynomial approximation to the expected welfare requires exponentially many queries, even when the set of feasible allocations is known to be downward-closed.
我们研究了不完全信息环境下福利最大化的黑盒约简,从机制设计到算法设计。给定oracle访问底层优化问题的算法,目标是模拟一个激励兼容机制。该机制将根据其相对于所提供算法的预期福利进行评估,其复杂性是通过在任何输入上模拟该机制所需的时间(和查询)来衡量的。虽然已知黑盒约简在许多没有先验的设置中是不可能的,但有先验的设置似乎更有希望:对于一般类别的福利最大化问题,贝叶斯激励兼容(BIC)机制设计有已知的约简。这种二分法回避了一个问题:哪些机制设计问题允许黑盒简化,哪些不允许?我们的主要结论是,黑盒机制设计在两个最简单的设置下是不可能的,这些设置没有被已知的积极结果所捕获。首先,对于将n件商品分配给单个买家的问题,该问题的估价在商品之间是可加的和独立的,受制于可行分配的向下封闭约束,我们证明了期望福利最大化不存在多时(in n) BIC黑盒缩减。其次,对于多个单参数代理的设置-其中已知多工时BIC减少-我们表明,当激励要求收紧到Max-In-Distributional-Range时,不存在多工时减少。在每种情况下,我们都表明,即使已知可行分配集是向下封闭的,实现预期福利的次多项式近似值也需要指数级的查询。
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引用次数: 4
The Supply and Demand Effects of Review Platforms 评鉴平台的供求效应
Pub Date : 2019-06-17 DOI: 10.2139/ssrn.3468278
Gregory Lewis, G. Zervas
Review platforms such as Yelp and TripAdvisor aggregate crowd-sourced information about users' experiences with products and services. We analyze their impact on the hotel industry using a panel of hotel prices, sales and reviews from five US states over a 10-year period from 2005--2014. Both hotel demand and prices are positively correlated with their average ratings on TripAdvisor, Expedia and Hotels.com, and such correlations have grown over our sample period from a statistical zero in the base year to a substantial level today: a hotel rated one star higher on all the platforms on average has 25% higher demand, and charges 9% more. We argue that the price increases are due to a combination of revenue management and re-pricing: increased demand from higher ratings shifts hotels along an upward sloping supply curve, and also causes small but significant changes in the supply curve itself. A natural experiment in our data that caused abrupt changes in the ratings of some hotels but not others, suggests that these associations are causal. Building on this causal interpretation, we estimate heterogenous treatment effects, showing that the impact of review platforms on hotels varies by organization form and hotel class. Specifically, we show that independent hotels that had little outside reputation prior to the entry of review platforms stand to gain more than chains.
点评平台如Yelp和TripAdvisor聚集了用户对产品和服务体验的信息。我们利用2005年至2014年10年间美国5个州的酒店价格、销售和评论来分析它们对酒店业的影响。酒店的需求和价格都与它们在TripAdvisor、Expedia和Hotels.com上的平均评分呈正相关,而且在我们的样本期内,这种相关性已经从基准年的统计为零增长到今天的显著水平:在所有平台上得分高1星的酒店,需求平均高出25%,收费高出9%。我们认为,价格上涨是由于收入管理和重新定价的结合:高评级带来的需求增加使酒店沿着一条向上倾斜的供应曲线移动,同时也导致供应曲线本身发生微小但显著的变化。在我们的数据中进行了一个自然实验,导致一些酒店的评级突然发生变化,而另一些则没有,这表明这些关联是因果关系。在这一因果解释的基础上,我们估计了异质性处理效应,表明点评平台对酒店的影响因组织形式和酒店类别而异。具体来说,我们表明,在点评平台进入之前几乎没有外部声誉的独立酒店将比连锁酒店获得更多。
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引用次数: 8
Prophet Inequalities for I.I.D. Random Variables from an Unknown Distribution 未知分布中i.i.d随机变量的先知不等式
Pub Date : 2019-06-17 DOI: 10.1145/3328526.3329627
J. Correa, Paul Dütting, Felix A. Fischer, Kevin Schewior
A central object in optimal stopping theory is the single-choice prophet inequality for independent, identically distributed random variables: given a sequence of random variables X1, ..., Xn drawn independently from a distribution F, the goal is to choose a stopping time τ so as to maximize α such that for all distributions F we have E[Xτ]≥α•E[maxt Xt]. What makes this problem challenging is that the decision whether τ=t may only depend on the values of the random variables X1, ..., Xt and on the distribution F. For a long time the best known bound for the problem had been α≥1-1/e≅0.632, but quite recently a tight bound of α≅0.745 was obtained. The case where F is unknown, such that the decision whether τ=t may depend only on the values of the random variables X1, ..., Xt, is equally well motivated but has received much less attention. A straightforward guarantee for this case of α≥1-1/e≅0.368 can be derived from the solution to the secretary problem, where an arbitrary set of values arrive in random order and the goal is to maximize the probability of selecting the largest value. We show that this bound is in fact tight. We then investigate the case where the stopping time may additionally depend on a limited number of samples from~F, and show that even with o(n) samples α≥1/e. On the other hand, n samples allow for a significant improvement, while O(n2) samples are equivalent to knowledge of the distribution: specifically, with n samples α≥1-1/e≅0.632 and α≥ln(2)≅0.693, and with O(n2) samples α≥0.745-ε for any ε>0.
最优停止理论的中心对象是独立同分布随机变量的单选择预言不等式:给定随机变量序列X1,…, Xn独立于分布F,目标是选择一个停止时间τ以使α最大化,使得对于所有分布F我们都有E[Xτ]≥α•E[max Xt]。使这个问题具有挑战性的是,决定τ=t是否可能仅取决于随机变量X1,…在很长一段时间里,这个问题最著名的界是α≥1-1/e = 0.632,但最近得到了一个严密的界α = 0.745。F未知的情况,使得τ=t的决定可能只取决于随机变量X1,…x同样积极,但受到的关注要少得多。对于这种α≥1-1/e = 0.368的情况,可以从秘书问题的解中得到一个直接的保证,其中任意一组值以随机顺序到达,目标是最大化选择最大值的概率。我们证明了这个边界实际上是紧的。然后,我们研究了停止时间可能额外依赖于来自~F的有限数量的样本的情况,并表明即使有o(n)个样本α≥1/e。另一方面,n个样本允许显著改进,而O(n2)个样本相当于对分布的了解:具体来说,n个样本α≥1-1/e = 0.632和α≥ln(2) = 0.693,并且对于任何ε>0, O(n2)个样本α≥0.745-ε。
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引用次数: 68
How Do Machine Learning Algorithms Perform in Predicting Hospital Choices?: Evidence from Changing Environments 机器学习算法在预测医院选择方面表现如何?:来自环境变化的证据
Pub Date : 2019-06-17 DOI: 10.1145/3328526.3329602
D. Raval, Ted Rosenbaum, N. Wilson
The proliferation of rich consumer-level datasets has led to the rise of the "algorithmic modeling culture" [2] wherein analysts treat the statistical model as a "black box" and predict choices using algorithms trained on existing datasets. In most cases, these evaluations of algorithmic prediction have focused on settings where individuals face the same choices over time. However, evaluating policy questions often involves modeling a substantial shift in the choice environment. For example, a health insurance reform may change the set of insurance products that consumers can buy, or a merger may alter the products available in the marketplace. For such questions, it is less obvious whether machine learning methods can usefully be applied. As Athey [1] remarks: [M]uch less attention has been paid to the limitations of pure prediction methods. When SML [supervised machine learning] applications are used "off the shelf" without understanding the underlying assumptions or ensuring that conditions like stability [of the environment] are met, then the validity and usefulness of the conclusions can be compromised.
丰富的消费者级数据集的激增导致了“算法建模文化”b[2]的兴起,其中分析师将统计模型视为“黑盒子”,并使用在现有数据集上训练的算法来预测选择。在大多数情况下,这些对算法预测的评估都集中在个体随着时间的推移面临相同选择的环境上。然而,评估政策问题通常涉及对选择环境中的重大转变进行建模。例如,健康保险改革可能改变消费者可以购买的保险产品集,或者合并可能改变市场上可用的产品。对于这样的问题,机器学习方法是否可以有效地应用就不那么明显了。正如Athey b[1]所说:[M]对纯预测方法的局限性给予的关注太少了。当SML[监督机器学习]应用程序在没有理解潜在假设或确保满足[环境]稳定性等条件的情况下被“现成”使用时,那么结论的有效性和有用性就会受到损害。
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引用次数: 4
The Value of Price Discrimination in Large Random Networks 大型随机网络中价格歧视的价值
Pub Date : 2019-06-17 DOI: 10.2139/ssrn.3368458
Jiali Huang, Ankur Mani, Zizhuo Wang
We study the value of price discrimination in large random networks. Recent trends in industry suggest that increasingly firms are using information about social network to offer personalized prices to individuals based upon their positions in the social network. In the presence of positive network externalities, firms aim to increase their profits by offering discounts to influential individuals that can stimulate consumption by other individuals at a higher price. However, the lack of transparency in discriminative pricing can reduce consumer satisfaction and create mistrust. Recent research has focused on the computation of optimal prices in deterministic networks under positive externalities. We would like to answer the question: how valuable is such discriminative pricing? We find, surprisingly, that the value of such pricing policies (increase in profits due to price discrimination) in very large random networks are often not significant. We provide the exact rates at which this value grows in the size of the random networks for different ranges of network densities.
研究了大型随机网络中价格歧视的价值。最近的行业趋势表明,越来越多的公司正在利用社交网络的信息,根据个人在社交网络中的位置,为他们提供个性化的价格。在正网络外部性存在的情况下,企业的目标是通过向有影响力的个人提供折扣来增加利润,从而刺激其他个人以更高的价格消费。然而,歧视性定价缺乏透明度会降低消费者满意度并产生不信任。最近的研究主要集中在正外部性下确定性网络中最优价格的计算。我们想回答这样一个问题:这种歧视性定价有多大价值?令人惊讶的是,我们发现,在非常大的随机网络中,这种定价政策(由于价格歧视而增加的利润)的价值往往并不显著。我们提供了这个值在不同网络密度范围内随随机网络大小增长的确切速率。
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引用次数: 16
Allocation for Social Good: Auditing Mechanisms for Utility Maximization 社会公益配置:效用最大化的审计机制
Pub Date : 2019-06-17 DOI: 10.1145/3328526.3329623
Taylor Lundy, Alexander Wei, Hu Fu, S. Kominers, Kevin Leyton-Brown
We consider the problem of a nonprofit organization ("center") that must divide resources among subsidiaries ("agents"), based on agents' reported demand forecasts, with the aim of maximizing social good (agents' valuations for the allocation minus any payments that are imposed on them). We investigate the impact of a common feature of the nonprofit setting: the center's ability to audit agents who receive allocations, comparing their actual consumption with their reported forecasts. We show that auditing increases the power of mechanisms for utility maximization, both in unit-demand settings and beyond: in unit-demand settings, we consider both constraining ourselves to an allocation function studied in past work and allowing the allocation function to vary; beyond unit demand, we adopt the VCG allocation but modify the payment rule. Our ultimate goal is to show how to leverage auditing mechanisms to maximize utility in repeated allocation problems where payments are not possible; we show how any static auditing mechanism can be transformed to operate in such a setting, using the threat of reduced future allocations in place of monetary payments.
我们考虑一个非营利组织(“中心”)的问题,它必须根据代理人报告的需求预测在子公司(“代理人”)之间分配资源,目的是最大化社会利益(代理人对分配的估值减去强加给他们的任何支付)。我们调查了非营利组织设置的一个共同特征的影响:该中心审计接受拨款的代理的能力,将他们的实际消费与报告的预测进行比较。我们表明,审计增加了效用最大化机制的力量,无论是在单位需求设置中还是在单位需求设置中:在单位需求设置中,我们考虑将自己限制在过去工作中研究的分配函数中,并允许分配函数变化;超出单位需求,我们采用VCG分配,但修改了支付规则。我们的最终目标是展示如何利用审计机制在无法支付的重复分配问题中最大化效用;我们将展示如何将任何静态审计机制转换为在这样的环境中运行,使用减少未来拨款的威胁来代替货币支付。
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引用次数: 7
期刊
Proceedings of the 2019 ACM Conference on Economics and Computation
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