Imitation processes with small mutations

This note characterizes the impact of adding rare stochastic mutations to an “imitation dynamic,” meaning a process with the properties that absent strategies remain absent, and non-homogeneous states are transient. The resulting system will spend almost all of its time at the absorbing states of the no-mutation process. The work of Freidlin and Wentzell [Random Perturbations of Dynamical Systems, Springer, New York, 1984] and its extensions provide a general algorithm for calculating the limit distribution, but this algorithm can be complicated to apply. This note provides a simpler and more intuitive algorithm. Loosely speaking, in a process with K strategies, it is sufficient to find the invariant distribution of a K×K Markov matrix on the K homogeneous states, where the probability of a transit from “all play i” to “all play j” is the probability of a transition from the state “all agents but 1 play i, 1 plays j” to the state “all play j”.     

Competition, Imitation and Growth with Step-by-Step Innovation

Is more intense product market competition and imitation good or bad for growth? This question is addressed in the context of an endogenous growth model with "step-by-step" innovations, in which technological laggards must first catch up with the leading-edge technology before battling for technological leadership in the future. In contrast to earlier Schumpeterian models in which innovations are always made by outsider firms who earn no rents if they fail to innovate and become monopolies if they do innovate, here we find: first, that the usual Schumpeterian effect of more intense product market competition (PMC) is almost always outweighed by the increased incentive for firms to innovate in order to escape competition, so that PMC has a positive effect on growth; second, that a little imitation is almost always growth-enhancing, as it promotes more frequent neck-and-neck competition, but too much imitation is unambiguously growth-reducing. The model thus points to complementary roles for competition (anti-trust) policy and patent policy.     

Complete information pivotal-voter model with asymmetric group size and asymmetric benefits

We analyze a standard pivotal-voter model under majority rule, with two rival groups of players, each preferring one of two public policies and simultaneously deciding whether to cast a costly vote, as in Palfrey and Rosenthal (1983). We allow the benefit of the favorite public policy to differ across groups and impose an intuitive refinement, namely that voting probabilities are continuous in the cost of voting to pin down a unique equilibrium. The unique cost-continuous equilibrium depends on a key threshold that compares the sizes of the two groups.     

Multi-player contests with asymmetric information

We consider imperfectly discriminating, common-value, all-pay auctions (or contests) in which some players know the value of the prize, others do not. We show that if the prize is always of positive value, then all players are active in equilibrium. If the prize is of value zero with positive probability, then there is some threshold number of informed players such that if there are less, all uninformed players are active, and otherwise all uninformed players are inactive.     

Core convergence with asymmetric information

We analyze the ex ante incentive compatible core for replicated private information economies. We show that any allocation in the core when the economy is replicated sufficiently often is approximately Walrasian for the associated Arrow–Debreu economy.     

模仿行为经济学分析——对经济波动的一种新解释

当前 ,世界经济面临衰退的威胁 ,科学解释经济波动具有重大的理论意义和现实意义。RBC理论或方法是当代西方经济学界解释经济波动最具前沿的一种理论或方法 ,也是宏观经济分析的方向。但存在明显缺陷。本文在修正RBC模型的基础上 ,首次建立模仿行为理论模型重新解释经济波动 ,并就中国政府在防止和治理经济波动的作用进行了独特的解释 ,认为政府所起的作用是示范人作用。     

基于模仿的技术扩散

对基于模仿的技术扩散重要研究进行了回顾。以信息不完全为出发点的理论研究主要包括传染病模型和贝叶斯学习模型等;以企业动机为出发点的研究主要包括两阶段的计量模型、门槛模型等。这些研究表明,信息传播所依赖的社会关系网络、技术引进者关于新技术信息的完整性以及企业规模的大小是决定技术扩散的影响因素。此外,关于技术扩散空间过程的一些重要研究,其本质就是传染病模型与门槛模型的空间版本。     

Access regulation with asymmetric termination costs

In many telecommunications markets incumbent providers enjoy a demand-side advantage over any entrant. However, market entrants may enjoy a supply-side advantage over the incumbent, since they are more efficient or operate on innovative technologies. Considering both a supply-side and a demand-side asymmetry, the present model analyzes the effect of two regulatory regimes: an access markup for a low cost network and reciprocal charges below the costs of a high cost network. Both regimes may have adverse effects on subscribers, market shares, and profits. It can be shown that an access markup is not generally beneficial and an access deficit not generally detrimental for the respective networks.     

On mixed markets with asymmetric information

In asymmetric information exchange economies involving both non-negligible and negligible agents, one should expect the failure of the private Core-Walras Equivalence Theorem. This paper shows that if “large” traders are similar to each other, then they lose their market power and hence the Equivalence Theorem can be restored. We also investigate on weaker equivalences among Walrasian expectations allocations, Aubin private core and private core allocations of the original mixed economy and the atomless one associated to it, without the assumption that all atoms are of the same type. Furthermore, extensions of Hervés-Moreno-Yannelis and Schmeidler Theorems (compare Hervés et al. in J Math Econ 41:844–856, 2005a; Schemidler in Econometrica 40:579–580, 1972) are given for differential information economies in which the feasibility constraints are imposed with an equality (exact feasibility).     

Consumer search with asymmetric price sampling

We explore asymmetries in the way consumers sample prices in a simple sequential search framework. In equilibrium, the price distribution of a firm catering to more local consumers first-order stochastically dominates that of its rival. Prices rise in the degree of asymmetry.     

Optimal auctions with asymmetric financial externalities

This paper studies optimal auction design with asymmetric linear financial externalities among bidders. When the matrix Γ that relates bidders? payoffs to their payments is nonsingular, the payment-related component in the design objective must equal a unique linear combination of its counterparts in bidder?s payoffs. If all multipliers of the linear combination are nonnegative, a modified Myerson procedure is discovered for deriving the optimal design. If any multiplier is negative, an arbitrarily high value can be achieved for design objective by setting proper fixed transfers to bidders. When the matrix Γ is singular, the unbounded optimum result typically prevails. We applied our method to auctions with cross shareholdings and charity auctions for revenue-maximizing and efficient designs.     

Ordered search with asymmetric product design

Two firms sell horizontally differentiated products on a platform; one product has generic design, whereas the other has polarized design. Consumers search sequentially for products and prices. We show that there always exists an equilibrium where firms correctly expect consumers to first search the product with polarized design. If the platform is able to choose a search order for consumers, generally it lets consumers search the product with polarized design first. The polarized–generic ordering can be achieved using a generalized English auction when product designs cannot be observed by the platform.     

Imitation and Experimentation in Changing Contests

This paper analyzes the equilibrium play of individuals that are randomly matched to play a contest where the dominant action changes over time. Under myopic decision making, players adopt imitation strategies similar to those observed in evolutionary models with sampling from past play in the population. If the players are patient, equilibrium strategies display elements of experimentation in addition to imitation. If the changes in the environment are infrequent enough, these strategies succeed in coordinating almost all of the players on the dominant action almost all of the time. The myopic rules, on the other hand, result in miscoordination for a positive fraction of time. Journal of Economic Literature Classification Numbers: C73, D83, D84.     

The Selection of Preferences Through Imitation

The paper presents a model in which a population of agents repeatedly play games against nature; the rules of behaviour followed are revised over time through a process of imitation. For binary decisions, imitation selects rules consistent with a preference relation of the kind proposed by SSB utility theory and regret theory. In general, this preference relation need not satisfy either independence or transitivity; we state conditions on imitation necessary for it to do so. For decisions over three or more options, the long-run tendency is for options that are maximally preferred in terms of SSB preferences to be chosen. If no maximally preferred option exists, the process of imitation may not converge.     

模仿经济学:一种新的方法论

创建模仿经济学的重大意义在于它为观察、解释经济现象和预测经济趋势提供了一种新的方法论、一种新的视角。作为一门边缘学科，模仿经济学的生命力在于它能借助社会心理学的科研成果，重新对主流经济学所关注的问题进行解释，并提出正确的政策建议。从方法论角度看，模仿经济学所提供的方法论立足于人的互动关系。从个体出发，同时又归结到群体，在理性与非理性的双重属性中观察经济现实，因而其用途极其广泛。     

Innovation,Imitation, and Intellectual Property Rights with International Capital Movement

This paper extends the established Helpman (1993 ) model by introducing international capital movement, and obtains new results concerning the welfare implications of tightening intellectual property rights (IPR) in the South. First, if separated capital markets in the North and the South are integrated, enforcement of IPR would have more desirable welfare effects in both regions. Second, when international capital movement is allowed, the North always gains from the tightening of IPR if the imitation rate is sufficiently high. This implies that the North's demand on the South to tighten IPR becomes stronger as the integration of international capital markets progresses.     

Approachability with bounded memory

We study Blackwell's approachability in repeated games with vector payoffs when the approaching player is restricted to use strategies with bounded memory: either strategies with bounded recall, or strategies that can be implemented by finite automata. Our main finding is that the following three statements are equivalent for closed sets. (i) The set is approachable with bounded recall strategies. (ii) The set is approachable with strategies that can be implemented with finite automata. (iii) The set contains a convex approachable set. Using our results we show that (i) there are almost-regret-free strategies with bounded memory, (ii) there is a strategy with bounded memory to choose the best among several experts, and (iii) Hart and Mas-Colell's adaptive learning procedure can be achieved using strategies with bounded memory.     

R&D cooperation with asymmetric spillovers

Abstract.  This paper analyses R&D cooperation with asymmetric spillovers. It is shown that the change in R&D by a firm following cooperation is proportional to the gap between the spillover rate transmitted by that firm and a critical level of spillovers. In consequence, cooperation increases total R&D investments when the average of firms' spillover rates is sufficiently high. Whereas with symmetric spillovers cooperation is always beneficial to firms, with asymmetric spillovers only a very limited range of spillovers makes cooperation beneficial to both firms. Asymmetries also create a potential conflict between maximizing total welfare and maximizing effective cost reduction. JEL classification: L13, O33