Approximate versus Exact Equilibria in Dynamic Economies

This paper develops theoretical foundations for an error analysis of approximate equilibria in dynamic stochastic general equilibrium models with heterogeneous agents and incomplete financial markets. While there are several algorithms that compute prices and allocations for which agents' first‐order conditions are approximately satisfied (“approximate equilibria”), there are few results on how to interpret the errors in these candidate solutions and how to relate the computed allocations and prices to exact equilibrium allocations and prices. We give a simple example to illustrate that approximate equilibria might be very far from exact equilibria. We then interpret approximate equilibria as equilibria for close‐by economies; that is, for economies with close‐by individual endowments and preferences. We present an error analysis for two models that are commonly used in applications, an overlapping generations (OLG) model with stochastic production and an asset pricing model with infinitely lived agents. We provide sufficient conditions that ensure that approximate equilibria are close to exact equilibria of close‐by economies. Numerical examples illustrate the analysis.     

Who's Who in Networks. Wanted: The Key Player

Finite population noncooperative games with linear‐quadratic utilities, where each player decides how much action she exerts, can be interpreted as a network game with local payoff complementarities, together with a globally uniform payoff substitutability component and an own‐concavity effect. For these games, the Nash equilibrium action of each player is proportional to her Bonacich centrality in the network of local complementarities, thus establishing a bridge with the sociology literature on social networks. This Bonacich–Nash linkage implies that aggregate equilibrium increases with network size and density. We then analyze a policy that consists of targeting the key player, that is, the player who, once removed, leads to the optimal change in aggregate activity. We provide a geometric characterization of the key player identified with an intercentrality measure, which takes into account both a player's centrality and her contribution to the centrality of the others.     

Uncertainty and Risk in Financial Markets

This paper considers a general equilibrium model in which the distinction between uncertainty and risk is formalized by assuming agents have incomplete preferences over state‐contingent consumption bundles, as in Bewley (1986). Without completeness, individual decision making depends on a set of probability distributions over the state space. A bundle is preferred to another if and only if it has larger expected utility for all probabilities in this set. When preferences are complete this set is a singleton, and the model reduces to standard expected utility. In this setting, we characterize Pareto optima and equilibria, and show that the presence of uncertainty generates robust indeterminacies in equilibrium prices and allocations for any specification of initial endowments. We derive comparative statics results linking the degree of uncertainty with changes in equilibria. Despite the presence of robust indeterminacies, we show that equilibrium prices and allocations vary continuously with underlying fundamentals. Equilibria in a standard risk economy are thus robust to adding small degrees of uncertainty. Finally, we give conditions under which some assets are not traded due to uncertainty aversion.     

Sales Force and Competition in Financial Product Markets: The Case of Mexico's Social Security Privatization

This paper examines how sales force impacts competition and equilibrium prices in the context of a privatized pension market. We use detailed administrative data on fund manager choices and worker characteristics at the inception of Mexico's privatized social security system, where fund managers had to set prices (management fees) at the national level, but could select sales force levels by local geographic areas. We develop and estimate a model of fund manager choice where sales force can increase or decrease customer price sensitivity. We find exposure to sales force lowered price sensitivity, leading to inelastic demand and high equilibrium fees. We simulate oft proposed policy solutions: a supply‐side policy with a competitive government player and a demand‐side policy that increases price elasticity. We find that demand‐side policies are necessary to foster competition in social safety net markets with large segments of inelastic consumers.     

COMPETING MATCHMAKING

We study how matchmakers use prices to sort heterogeneous participants into competing matching markets and how equilibrium outcomes compare with monopoly in terms of prices, matching market structure, and sorting efficiency under the assumption of complementarity in the match value function. The role of prices to facilitate sorting is compromised by the need to survive price competition. We show that price competition leads to a high‐quality market that is insufficiently exclusive. As a result, the duopolistic outcome can be less efficient in sorting than the monopoly outcome in terms of total match value in spite of servicing more participants. (JEL: C7, D4)     

Virtual Determinacy in Overlapping Generations Models

We reappraise the significance and robustness of indeterminacy in overlapping‐generations models. In any of Gale's example economies with an equilibrium that is not locally unique, for instance, perturbing the economy by judiciously splitting each of Gale's goods into two close substitutes restricts that indeterminacy to each period's allocation of consumption between those substitutes. In particular, prices, interest rates, the commodity value of nominal savings (including money), and utility levels become determinate. Any indeterminacy of equilibrium consumption in the perturbed economy is thus insignificant to consumers, and some forecasting and comparative‐statics policy exercises become possible.     

Self‐Control and the Theory of Consumption

To study the behavior of agents who are susceptible to temptation in infinite horizon consumption problems under uncertainty, we define and characterize dynamic self‐control (DSC) preferences. DSC preferences are recursive and separable. In economies with DSC agents, equilibria exist but may be inefficient; in such equilibria, steady state consumption is independent of initial endowments and increases in self‐control. Increasing the preference for commitment while keeping self‐control constant increases the equity premium. Removing nonbinding constraints changes equilibrium allocations and prices. Debt contracts can be sustained even if the only feasible punishment for default is the termination of the contract.     

Efficiency,Equilibrium, and Asset Pricing with Risk of Default

We introduce a new equilibrium concept and study its efficiency and asset pricing implications for the environment analyzed by Kehoe and Levine (1993) and Kocherlakota (1996). Our equilibrium concept has complete markets and endogenous solvency constraints. These solvency constraints prevent default at the cost of reducing risk sharing. We show versions of the welfare theorems. We characterize the preferences and endowments that lead to equilibria with incomplete risk sharing. We compare the resulting pricing kernel with the one for economies without participation constraints: interest rates are lower and risk premia depend on the covariance of the idiosyncratic and aggregate shocks. Additionally, we show that asset prices depend only on the valuation of agents with substantial idiosyncratic risk.     

Information Aggregation in Dynamic Markets With Strategic Traders

This paper studies information aggregation in dynamic markets with a finite number of partially informed strategic traders. It shows that, for a broad class of securities, information in such markets always gets aggregated. Trading takes place in a bounded time interval, and in every equilibrium, as time approaches the end of the interval, the market price of a “separable” security converges in probability to its expected value conditional on the traders' pooled information. If the security is “non‐separable,” then there exists a common prior over the states of the world and an equilibrium such that information does not get aggregated. The class of separable securities includes, among others, Arrow–Debreu securities, whose value is 1 in one state of the world and 0 in all others, and “additive” securities, whose value can be interpreted as the sum of traders' signals.     

RISK AVERSION,WEALTH, AND BACKGROUND RISK

We use household survey data to construct a direct measure of absolute risk aversion based on the maximum price a consumer is willing to pay for a risky security. We relate this measure to consumer's endowments and attributes and to measures of background risk and liquidity constraints. We find that risk aversion is a decreasing function of the endowment—thus rejecting CARA preferences. We estimate the elasticity of risk aversion to consumption at about 0.7, below the unitary value predicted by CRRA utility. We also find that households' attributes are of little help in predicting their degree of risk aversion, which is characterized by massive unexplained heterogeneity. We show that the consumer's environment affects risk aversion. Individuals who are more likely to face income uncertainty or to become liquidity constrained exhibit a higher degree of absolute risk aversion, consistent with recent theories of attitudes toward risk in the presence of uninsurable risks. (JEL: D1, D8)     

发明人网络结构与组织合作网络位置

以社会网络理论为基础,从跨层次视角分析组织内外部合作网络之间的作用机制,提出组织内部发明人合作网络中心势和结构洞数量,对其嵌入组织间合作网络中心位置具有直接影响和交互作用,并运用2003~2017年无人驾驶技术领域中,6029条无人驾驶技术专利数据进行实证检验。研究显示:组织内部发明人合作网络中心势,负向影响组织嵌入外部研发合作网络的中心位置;组织内部发明人合作网络结构洞数量,正向影响组织嵌入外部研发合作网络的中心位置;二者交互对组织嵌入组织间合作网络中心位置具有负向作用。     

Quadratic Concavity and Determinacy of Equilibrium

One of the central features of classical models of competitive markets is the generic determinacy of competitive equilibria. For smooth economies with a finite number of commodities and a finite number of consumers, almost all initial endowments admit only a finite number of competitive equilibria, and these equilibria vary (locally) smoothly with endowments; thus equilibrium comparative statics are locally determinate. This paper establishes parallel results for economies with finitely many consumers and infinitely many commodities. The most important new condition we introduce, quadratic concavity, rules out preferences in which goods are perfect substitutes globally, locally, or asymptotically. Our framework is sufficiently general to encompass many of the models that have proved important in the study of continuous‐time trading in financial markets, trading over an infinite time horizon, and trading of finely differentiated commodities.     

消费者多方购买行为与企业R&D策略博弈分析

通过构建完全信息博弈模型,研究具有网络外部性的产品市场中,在存在消费者多方购买行为时企业的研发策略和创新动机,并深入分析多方购买者比例大小和网络外部性强度对企业研发投资水平的影响。在市场中存在多方购买行为时均衡结果表明:(i)企业有动机进行研发投资;(ii)研发企业均衡价格、需求以及利润均高于不研发企业;(iii)在差异度系数和投资系数都充分大时研发企业最优研发投入随着多方购买者比例的增加而增大。最后通过具体算例分析知道:在考虑多方购买条件下,市场中存在研发时消费者总剩余和社会总福利高于市场中不存在研发时的情形。     

在相关系数暧昧环境下的市场微观结构研究

投资者对相关系数的认知存在暧昧性从一个新的视角解释了金融市场中投资者有限参与现象。为了研究如何从市场微观结构设计的角度降低投资者的认知暧昧性,提高其市场参与程度,本文假设所研究经济体中存在两个证券发行市场：投资者认知暧昧性较低的A市场和较高的B市场。当两种风险资产分别在不同的证券市场上发行时,投资者的资产组合决策将会不同,从而各市场的均衡状态和风险资产的均衡价格也不相同。考虑公司上市成本和收益,理性的公司管理者将选择均衡价格较高的市场来发行证券。本文的研究发现,最大相关系数暧昧性、投资者结构等因素的变化对公司选择证券发行市场有重要影响,说明了通过市场微观结构设计来降低投资者对市场认知的暧昧性具有重要意义。市场微观结构特征,如严格的证券发行标准、充分的信息披露等旨在提高市场透明度的设计,能够在一定程度上降低投资者的认知暧昧性,提高其市场参与程度,以提高金融市场流动性,使公司股票的市场均衡价格更好地反映其资产的真实价值。我们的研究还发现,为满足不同特征上市公司的融资需求,需要建立多层次资本市场。     

How Does Centrality in Coopetition Networks Matter? An Empirical Investigation in the Mobile Telephone Industry

This research examines how a firm's position in a coopetitive network (formed through cooperation among firms within an industry) influences the extent of the firm's competitive aggressiveness and market performance. The authors collected data on the competitive and cooperative actions of firms in the mobile telephone industry from 2000 to 2006, using structured content analysis of news reports. The results show that the centrality of a firm in a coopetitive network contributes to the firm's competitive aggressiveness through increased volume and variety of competitive actions. Further, the more central a firm is in the network, the greater is its market performance. Firms that undertake more volume and variety of competitive actions improve their market performance. Overall, these results show that being in a central position in a coopetition network is quite advantageous for the firm.     

The Economics of Labor Coercion

The majority of labor transactions throughout much of history and a significant fraction of such transactions in many developing countries today are “coercive,” in the sense that force or the threat of force plays a central role in convincing workers to accept employment or its terms. We propose a tractable principal–agent model of coercion, based on the idea that coercive activities by employers, or “guns,” affect the participation constraint of workers. We show that coercion and effort are complements, so that coercion increases effort, but coercion always reduces utilitarian social welfare. Better outside options for workers reduce coercion because of the complementarity between coercion and effort: workers with a better outside option exert lower effort in equilibrium and thus are coerced less. Greater demand for labor increases coercion because it increases equilibrium effort. We investigate the interaction between outside options, market prices, and other economic variables by embedding the (coercive) principal–agent relationship in a general equilibrium setup, and studying when and how labor scarcity encourages coercion. General (market) equilibrium interactions working through the price of output lead to a positive relationship between labor scarcity and coercion along the lines of ideas suggested by Domar, while interactions those working through the outside option lead to a negative relationship similar to ideas advanced in neo‐Malthusian historical analyses of the decline of feudalism. In net, a decline in available labor increases coercion in general equilibrium if and only if its direct (partial equilibrium) effect is to increase the price of output by more than it increases outside options. Our model also suggests that markets in slaves make slaves worse off, conditional on enslavement, and that coercion is more viable in industries that do not require relationship‐specific investment by workers.     

Optimal pricing for group buying with network effects

In this paper, we analyze online group-pricing mechanisms for sellers and compare them with the option of selling only to individuals. We formulate the demand for group buying and individual buying (GB and IB, respectively) based on the utility a consumer attains from each environment considering two specific types of externalities unique to our problem. First, we assume that consumers receive positive “network effects” from GB, i.e., they obtain utility from shopping with others because of information exchange and collective support. Second, they encounter a negative externality of group buying because of inconvenience costs and delays in receiving the products. The two types of externalities lead to distorted demand, which in turn affects prices and profits. We analyze the optimal and equilibrium strategies for a seller operating in monopoly, duopoly, and multiple-firm competition. We derive the equilibrium strategies and show the existence of a Nash Equilibrium under competition of multiple firms. In addition, we show that positive network effects from group buying often outweigh the negative externalities arising from costs.     

Leverage and Default in Binomial Economies: A Complete Characterization

Our paper provides a complete characterization of leverage and default in binomial economies with financial assets serving as collateral. Our Binomial No‐Default Theorem states that any equilibrium is equivalent (in real allocations and prices) to another equilibrium in which there is no default. Thus actual default is irrelevant, though the potential for default drives the equilibrium and limits borrowing. This result is valid with arbitrary preferences and endowments, contingent or noncontingent promises, many assets and consumption goods, production, and multiple periods. We also show that only no‐default equilibria would be selected if there were the slightest cost of using collateral or handling default. Our Binomial Leverage Theorem shows that equilibrium Loan to Value (LTV) for noncontingent debt contracts is the ratio of the worst‐case return of the asset to the riskless gross rate of interest. In binomial economies, leverage is determined by down risk and not by volatility.     

Does Market Incompleteness Matter?

This paper argues that incompleteness of intertemporal financial markets has little effect (on welfare, prices, or consumption) in an economy with a single consumption good, provided that traders are long–lived and patient, a riskless bond is traded, shocks are transitory, and there is no aggregate risk. In an economy with aggregate risk, a similar conclusion holds, provided traders share the same CRRA utility function and the right assets are traded. Examples demonstrate that these conclusions need not hold if the wrong assets are traded or if the economy has multiple consumption goods.     

How Managers Talk about their Consumption of Popular Management Concepts: Identity,Rules and Situations

This paper analyses how top managers account for their consumption of popular management concepts. By ‘consumption’ we refer to managers acting as active users of popular management concepts within their organizations. After reviewing the relevant literature, we argue that the logic of appropriateness is a better theoretical perspective to view, understand and analyse managers' accounts of concept consumption than is the logic of consequence. We apply this perspective to extensive interviews we conducted with top managers in Germany. Based on the managers' own accounts of how they understand and apply popular management concepts, we identified four discourse categories: (1) learning from others' experiences, (2) controlling organizational change, (3) gaining external legitimacy and (4) collective sensemaking. We argue that these discourse categories all draw on the social norm of rationality central to managerial identity, while differing in socially defined rules about how rationality is realized in typical management situations. Our findings strongly encourage researchers, when investigating popular management concepts in the future, to take into account the situational nature of rationality that circumstantiates the consumption of concepts.