Competition and confidentiality: Signaling quality in a duopoly when there is universal private information

We model non-cooperative signaling by two firms that compete over a continuum of consumers, assuming each consumer has private information about the intensity of her preferences for the firms' respective products and each firm has private information about its own product's quality. We characterize a symmetric separating equilibrium in which each firm's price reveals its respective product quality. We show that the equilibrium prices, the difference between those prices, the associated outputs, and profits are all increasing functions of the ex ante probability of high safety. If horizontal product differentiation is sufficiently great then equilibrium prices and profits are higher under incomplete information about quality than if quality were commonly known. Thus, while signaling imposes a distortionary loss on a monopolist using price to signal quality, duopolists may benefit from the distortion as it can reduce competition. Finally, average quality is lower since signaling quality redistributes demand towards low-quality firms.     

Price signaling and the strategic benefits of price rigidities

We analyze trade between a perfectly informed price setting party (seller) and an imperfectly informed price taker (buyer). Differently from most of the literature, we focus on the case in which, under full information, it would be inefficient to trade goods of sufficiently poor quality. We show that the unique equilibrium surviving D1 is characterized by market breakdown, although trade would be mutually beneficial in some state of nature. This occurs independently of the precision of the information available to the buyer. The model thus implies that signaling through prices may exacerbate the effect of adverse selection rather than mitigate it. Under D1, the seller would always benefit from committing to prices that do not reveal her information. We develop this intuition by analyzing the strategic advantages of price rigidities. We show that price rigidities help restore trade and could even enhance effectiveness of prices as signals of quality.     

网购市场鱼龙混杂现象的经济学解释：基于二维不对称信息的视角

网络购物市场存在商品鱼龙混杂的典型现象：高价格的商品不一定高质量，低价格的商品也不一定低质量，表现出明显的信息不对称特征。文章基于网络购物市场所存在的两个维度不对称信息的特征事实，即厂商在产品质量与产品生产成本两个方面拥有私有信息，通过构建二维不对称信息的分析框架，从市场均衡的视角首次解释了上述现象的经济机理。分析表明，由于二维不对称信息的存在，消费者和厂商决策的互动过程使得市场上产品价格与质量不再具有单调递增关系，从而网络购物市场可能出现鱼龙混杂的市场均衡，文章证明了这一均衡在合理的条件下是存在的。文章通过比较静态分析考察了市场环境的变化如何影响商品质量的价格信号显示效率以及消费者购买行为，并考察了网络购物行业商家披露信息、消费者对于商家的反馈评分机制和保证退货等手段对于消除商品鱼龙混杂现象的有效性，为进一步规范发展我国网络购物行业提供了参考。     

Effect of Short‐sale Constraints on Stock Price Manipulation

This paper examines the effect of short‐sale constraints on the stock price manipulation of an insider, who is subject to mandatory disclosure rules. We show that the privately informed insider may manipulate by trading against his or her information when short selling is banned. We find that stock price movement is asymmetric in the sense that prices fall by a larger percentage than they rise. In addition, we prove that removing short‐sale constraints increases price volatility. Finally, we explore the welfare implications of short‐sale constraints.     

Vertical Product Differentiation When Quality is Scarce: The Case of n > 2 Firms

This paper describes a model of vertical product differentiation in which more than two firms compete in quality and price. Quality is of fixed supply, so firms participate in an auction to attain it. Firms then simultaneously choose prices. The paper determines equilibrium bids in the quality auction and the Bertrand equilibrium prices. In equilibrium one firm attains all the units of quality, but pays a price such that it, like the minimum-quality firms, earns zero profits. Aggregate welfare is computed, and is shown to decrease as competition increases.     

A choice of auction format in seller cheating: a signaling game analysis

In this paper, we examine which auction format, first-price or second-price, a seller will choose when he can profitably cheat in a second price auction by observing all bids by possible buyers and submitting a shill bid as pretending to be a buyer. We model this choice of auction format in seller cheating as a signaling game in which the buyers may regard the selection of a second price auction by the seller as a signal that he is a shill bidder. By introducing trembling-hand perfectness as a refinement of signaling equilibrium, we find two possible strictly perfect signaling equilibria. One is a separating equilibrium in which a noncheating honest seller selects a first price auction and a cheating seller does a second price auction. In another pooling equilibrium, however, both cheating and non-cheating sellers select a second price auction. The conclusion that a seller chooses a second price auction even if he cannot cheat is in contrast to the previous literature, which focused on the case of independent values. We thank an anonymous referee for useful comments that have improved the paper. This research was partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (B) 15310023 and (C) 18530139.     

股票网络平台中的噪音会影响股价同步性吗

股价同步性是衡量资本市场信息效率的重要指标。股价同步性的影响机制一直以来都是金融研究的热点问题。本文使用文本分析的方法,通过机器学习度量了东方财富股吧中股民发帖评论中的非理性噪音,检验了股票网络平台中的噪音与股价同步性之间的关系。研究发现：第一,股票网络平台中的噪音会促使投资者做出非理性的投资决策,进而降低股价变动的同步性。噪音评论占全部评论的比例越高,上市公司的股价同步性越低,而且两者之间呈现倒U型的非线性关系。第二,公司个股新闻与公告数量的增加、分析师关注度的提高与外部审计质量的提升,均可以减弱股票网络平台中的噪音对股价同步性的影响。本文关注网络新媒体中的噪音对股价同步性的影响,研究结论对于监管部门加强网络信息监测以及上市公司进一步完善信息披露渠道具有现实意义。     

Price Competition and Consumer Externalities in a Vertically Differentiated Duopoly with Information Disparities

In this paper, we extend the model of vertical product differentiation to consider information disparities about quality differences and their effects on price competition. If uninformed consumers overestimate vertical differentiation, asymmetric information is a source of market power and informed consumers exert positive externalities on high quality product purchasers and negative externalities on low quality product purchasers. Such a result is consistent with the fact that information undermines brand. If uninformed consumers are skeptical, adverse selection issues arise and market demands may be perfectly inelastic to prices. With elastic demands equilibrium prices may be either distorted downwards or reflect real quality if the share of informed consumers is suffciently high. Therefore, with skeptical consumers firms may want either to signal quality or subsidize information provision.     

Coalition-proof Bertrand equilibria

Summary. This paper examines the coalition-proof Nash equilibria of a Bertrand model of price competition where firms supply all demand. When firms are asymmetric we prove existence and provide a sufficient condition for uniqueness. For symmetric firms, we show that an equilibrium is necessarily unique. We also examine whether this unique equilibrium outcome is implementable through a sequential move game where the firms take turns at announcing prices. Finally we examine the limiting property of such equilibria as the number of firms go to infinity.Received: 20 March 2002, Revised: 5 August 2003JEL Classification Numbers: D43, D41, L13.Correspondence to: Kunal SenguptaWe are deeply indebted to an anonymous referee for very helpful and incisive comments that led to substantial improvements in the paper. We also gratefully acknowledge the hospitality of the Department of Finance, Hong Kong University of Science and Technology where much of the work on this paper was carried out.     

Reserve price signaling

In a general auction model in which bidders’ signals are affiliated, we characterize the unique separating equilibrium in which the seller can use reserve prices to credibly signal her private information. When the buyers’ signals are independent, the optimal reserve price is shown to be increasing in the number of bidders under certain conditions. We also demonstrate that the probability that the item is sold at the reserve price can increase as the number of bidders increases, which indicates a more central role for reserve prices than perceived in the standard auction models.     

Price normalization under imperfect competition

In general equilibrium models of imperfect competition the equilibria depend on how prices are normalized. This note shows that a price normalization preserves convexity properties if and only if prices are measured in terms of a fixed commodity bundle. I am grateful to an anonymous referee for helpful comments, inspiring a simplification in the proof of the main result, and the argument in the Remark.     

Pricing and signaling with frictions

We study a market where each seller chooses the quality and price of goods and the number of selling sites. Observing sellers? choices of prices and sites, but not quality, buyers choose which site to visit. A seller?s choices of prices can direct buyers? search and signal quality. A unique equilibrium exists and is separating. When the quality differential is large, the equilibrium implements the efficient allocation with public information. Otherwise, the quality of goods and/or the number of sites created is inefficient, due to a conflict between the search-directing and signaling roles of prices.     

监督制度、市场信息与协议地价-基于杭州市土地储备制度改革的经验

对杭州市1992-2001年城市土地市场中的367宗土地交易资料的分析表明,监督制度和市场信息是影响协议地价与招标、拍卖标底地价的主要因素.在土地市场发育不完善的1992年,标底地价与该宗地相对应的基准地价不存在差异.监督制度的不健全,导致1995年协议地价低于基准地价.监督制度比较完善、土地市场发育比较成熟的1999-2001年,协议地价、标底地价都显著的高于基准地价.     

Policy consequences of limited cognitive ability

This paper analyses the welfare effects of price restrictions on private contracting in a world where agents have a limited cognitive ability. We deal with that by assuming that people compute the costs and benefits of entering a transaction with an error. We first discuss an example of an auction that will attract the least efficient buyers, because these are those who have made the largest mistake. We then study the case for government intervention when the government knows the distribution of true costs and benefits as well as that of errors. By imposing constraints on transaction prices, the government eliminates some that are on average inefficient - because the price signals that one of the parties has typically grossly overestimated its benefit from participation. This policy may increase aggregate welfare even though some of the transactions being blocked are actually efficient.JEL Classification: D81, J38, K31Gilles Saint-Paul: This paper is based on my Spanish Economic Review lecture at the Spanish Economic Association meeting, Salamanca, December 2002. I am grateful to the organizers for inviting me, and to participants and especially Juan Dolado for their useful comments.     

Commitment and price competition in a dynamic differentiated-product duopoly

This paper characterizes linear Markov-perfect equilibrium in a duopolistic environment where firms engage in dynamic price competition. Firms have constant (but potentially different) marginal costs and produce differentiated products. We show that, for the case of linear demand, dynamically stable Markov-perfect equilibrium prices are strictly higher than one-shot Nash equilibrium prices, but lower than fully collusive (monopoly) prices. We provide closed-form solutions for the Markov-perfect equilibrium prices which, in principle, can be estimated given data on firm demand and costs. Our results suggest that static two-stage models of price commitment are on reasonably solid ground in that they might be viewed as a reduced form for more complicated dynamic models.     

Search, Bargaining, Money, and Prices Under Private Information

This paper presents a model of money and search where bargaining determines prices and the quality of goods is private information. It studies how a lemons problem affects the purchasing power of money. There are multiple, Pareto-ranked equilibria. The superior equilibrium, where no lemons are produced, exists even if information about quality is relatively scarce. In other equilibria, there is price dispersion, and uninformed buyers pay higher prices than informed buyers for all goods. Taxing money balances (a proxy for inflation) makes buyers less selective, thus reducing the average quality of supply and the premium paid for known quality.     

Coalition-proof supply function equilibria under capacity constraints

Whereas in the absence of capacity constraints the Cournot outcome is the unique coalition-proof supply function equilibrium outcome, the presence of capacity constraints may enlarge the set of equilibrium outcomes. Interestingly, if capacities are sufficiently asymmetric the new equilibrium prices are below the Cournot price. These results have important implications for merger and privatization policies: specifically, capacity divestiture will not necessarily imply lower market prices.This article is based on the second chapter of my PhD dissertation. I benefited from the comments and suggestions of Diego Moreno and Bill Hogan. I thank three anonymous referees for helpful comments. Seminar audiences at Carlos III and Harvard are gratefully acknowledged. The author is currently a Repsol YPF fellow at the Harvard John F. Kennedy School of Government. I am grateful to the Repsol YPF-Harvard Fellowship Program for financial support.     

Equilibrium without prices: A central issue in pareto’smanuale

Pareto in hisManuale asserts that the price concept is inessential for the notion of equilibrium. This view deeply contrasts with the Arrow-Debreu’s dominant approach of Walrasian derivation. This identifies general equilibrium with a system of prices at which the decentralized choices of economic agents match. In this paper the author justifies and gives substance to the Paretian point of view. The differential merit of the Paretian approach is its independence of assumptions of price taking and of convexity in preferences and in production possibility sets. These assumptions are necessary, in the walrasian framework, only to maintain the centrality of prices, but they clash against the request of realism. (JEL:BOO, D51, D60)     

Consumption choice and asset pricing with a non-price-taking agent

Summary. This paper develops a pure-exchange model to study the consumption-portfolio problem of an agent who acts as a non-price-taker, and to analyze the implications of his behavior on equilibrium security prices. The non-price-taker is modeled as a price leader in all markets; his price impact is then recast as a dependence of the Arrow-Debreu prices on his consumption, allowing a tractable formulation. Besides the aggregate consumption, the endowment of the non-price-taker appears as an additional factor in driving equilibrium allocations and prices. Comparisons of equilibria between a price-taking and a non-price-taking economy are carried out. Received: March 29, 1996; revised version October 29, 1996     

Union-oligopoly bargaining and entry deterrence: a reassessment of limit pricing

This paper introduces wage bargaining in the framework of Milgrom and Roberts (Econometrica 50(2):443–459, 1982) where the workers’ reservation wage is the private information parameter critical for entry. We show that entry threat significantly distorts the wage, which in some cases adversely affects the firm’s ability to signal through price. Consequently, the separating equilibrium (in price) does not always exist. If, however, wage agreements are made public, signalling occurs with or without distortions in wage depending on whether the union’s bargaining power is high or low. Pooling equilibrium also exists and it features similar distortions. We also examine which signal, wage or price, generates greater social welfare. We would like to thank two referees for their helpful comments and suggestions. This paper is partially based on a chapter of Pal’s PhD thesis done at Indira Gandhi Institute of Development Research (IGIDR), India. For remaining errors we are solely responsible.