An evolutionary model of speculative attacks

We build an evolutionary model of currency crises incorporating learning through imitation and experimentation by heterogeneous agents. Foreign currency speculators in the model interact and learn over time through experimentation. Drawing on results from game theory, we show that the resulting dynamic converges to a unique long run equilibrium, in which the currency is “attacked” if the economic fundamentals are sufficiently adverse. Evolutionary selection is thus shown as a way to resolve the issue of indeterminacy of equilibria associated with models of currency crises.JEL Classification: C63, F31, D83, C72I am grateful to Jasmina Arifovic, Peter Garber, Pravin Krishna, Blake LeBaron, Nidhiya Menon, Srinivas Thiruvadanthai and Tiemen Woutersen for useful remarks and suggestions. All errors remain my own.     

The macroeconomic risks of undesirably low inflation

This paper investigates the macroeconomic risks associated with undesirably low inflation using a medium-sized New Keynesian model. We consider different causes of persistently low inflation, including a downward shift in long-run inflation expectations, a fall in nominal wage growth, and a favorable supply-side shock. We show that the macroeconomic effects of persistently low inflation depend crucially on its underlying cause, as well as on the extent to which monetary policy is constrained by the zero lower bound. Finally, we discuss policy options to mitigate these effects.     

Schumpeterian endogenous growth theory and evolutionary economics

In this paper, we aim to discuss whether Schumpeterian models of endogenous growth can accommodate Schumpeters vision of development through creative destruction. Taking a methodological approach, our focus is on individual decision-making, technology, general equilibrium and welfare, and steady state dynamics as the fundamental principles underlying endogenous growth theory. In particular, the Aghion-Howitt model of Schumpeterian growth in various extended versions is analyzed in the light of Schumpeters work. Therefore, we also try to root Schumpeters work in historical context. We find endogenous growth theory far from carrying Schumpeters idea of an evolutionary approach to change and development. Rather the emergence of numerous models of an evolutionary type can be observed to provide for the formal structure appropriate to keeping Schumpeters legacy alive.JEL Classification: B1, B2, B4, O3, O4Corespondence to: Thomas Kuhn     

Stochastic evolution with slow learning

Summary. This paper studies the extent to which diffusion approximations provide a reliable guide to equilibrium selection results in finite games. It is shown that they do for a class of finite games with weak learning provided that limits are taken in a certain order. The paper also shows that making mutation rates small does not in general select a unique equilibrium but making selection strong does. Received: January 19, 2000; revised version: September 25, 2000     

Correlated equilibrium in evolutionary models with subpopulations

We study a version of the multipopulation replicator dynamics, where each population is comprised of multiple subpopulations. We establish that correlated equilibrium is a natural solution concept in this setting. Specifically, we show that every correlated equilibrium is equivalent to a stationary state in the replicator dynamics of some subpopulation model. We also show that every interior stationary state, Lyapunov stable state, or limit of an interior solution is equivalent to a correlated equilibrium. We provide an example with a Lyapunov stable limit state whose equivalent correlated equilibrium lies outside the convex hull of the set of Nash equilibria. Finally, we prove that if the matching distribution is a product measure, a state satisfying any of the three conditions listed above is equivalent to a Nash equilibrium.     

通货膨胀目标制度在我国实施的可行性分析

20世纪90年代以来,由于通货膨胀目标制(Inflation Targeting,以下又简称通胀目标制)被越来越多的国家采用,使得通胀目标制成为近年西方货币经济学领域最热门的研究课题之一。从传统的以控制货币供应量为主的货币目标法(Monetary'Targeting)和以稳定汇率为主的汇率目标法(Exchange rate Targeting)到明确公布通货膨胀目标的通胀目标制是一个货币政策方面的重大转变。本文主要分析了我国实施通胀目标制的可行性,并提供相关的政策建议。     

Endogenous fluctuations under evolutionary pressure in Cournot competition

An evolutionary game theoretic model of Cournot competition is investigated. Individuals choose from a finite set of different behavioral rules. Each rule specifies the quantity to be produced in the current period as a function of past quantities. Using more sophisticated rules may require extra information costs. Based upon realized payoffs, the fractions of the population choosing a certain behavioral rule are updated according to the replicator equation with noise. The long-run behavior of the evolutionary system consisting of the population dynamics coupled with the quantity dynamics of the Cournot game may be complicated and endogenous fluctuations may arise. We consider a typical example where firms can choose between two rules: the Nash rule and the best-reply rule. We show that a homoclinic tangency between the stable and unstable manifold of the equilibrium occurs as evolutionary pressure increases, implying bifurcation routes to complicated dynamics and strange attractors.     

解读演化经济学的兴起——兼论演化经济学的现状与未来发展

演化经济学的兴起主要有三个原因:西方主流经济学的范式危机;自然科学的发展;社会科学领域演化思想的积累与发展.演化经济学最近的前沿研究集中于进行演化建模,对复杂性进行测量,讨论技术与制度的协同演化等几个方面.拓展对多时期动态过程的研究,将演化经济学与制度经济学、马克思主义经济学、博弈理论等进行创造性综合,更多关注学科语言的凝炼和理论建模工作是演化经济学的未来发展方向.     

On economic applications of evolutionary game theory

Evolutionary games have considerable unrealized potential for modeling substantive economic issues. They promise richer predictions than orthodox game models but often require more extensive specifications. This paper exposits the specification of evolutionary game models and classifies the possible asymptotic behavior for one and two dimensional models.     

The optimal neglect of inflation: An alternative interpretation of UK monetary policy during the “Great Moderation”

This paper argues that UK monetary policymakers did not respond to the inflation rate during most of the “Great Moderation” that ran from the early 1990s to the mid-2000s. We derive a generalisation of the New Keynesian Phillips curve in which inflation is a non-linear function of the output gap and show that the optimal response of the policy rule to inflation depends on the slope of the Phillips curve; if this is flat, manipulation of aggregate demand through monetary policy does not affect inflation and so policymakers cannot affect inflation. We estimate the monetary policy rules implied by a variety of alternative Phillips curves; our preferred model is based on a Phillips curve that is flat when output is close to equilibrium. We find that policy rates do not respond to inflation when the output gap is small, a situation that characterised most of the “Great Moderation” period.     

The expected inflation channel of government spending in the postwar U.S.

There exist sticky price models in which the output response to a government spending change can be large if the central bank is nonresponsive to inflation. According to this “expected inflation channel,” government spending drives up expected inflation, which in turn, reduces the real interest rate and leads to an increase in private consumption. This paper examines whether the channel was important in the post-WWII U.S., with particular attention to the 2009 Recovery Act period. First, we show that a model calibrated to have a large output multiplier requires a large response of expected inflation to a government spending shock. Next, we show that this large response is inconsistent with structural vector autoregression evidence from the Federal Reserve׳s passive policy period (1959–1979). Then, we study expected inflation measures during the Recovery Act period in conjunction with a panel of professional forecaster surveys, a cross-country comparison of bond yields and fiscal policy news announcements. We show that the expected inflation response was too small to engender a large output multiplier.     

Schumpeter's theory of economic evolution: a Darwinian interpretation

A general Darwinian framework is employed to arrive at an interpretation of Schumpeter's work that brings out clearly its specific evolutionary aspects. Schumpeter's theory of economic evolution is seen to be still highly relevant to evolutionary economics, because it sheds light on some fundamental issues: the relationship between evolutionary theory and equilibrium analysis, the usefulness of Darwinian theory for economics, and the precise nature of the evolutionary forces at work in economic systems.     

Institutional change from an evolutionary perspective: the Mexican experience

The fall of the Institutional Revolutionary Party (PRI) in July 2000 marked a milestone in Mexico’s political history. Throughout its 71 years of incumbency, the PRI had incarnated the set of social, political and economic institutions of the country to the extent of becoming synonymous with governance and stability. Using a simple model in which institutional change is the result of the strategic interaction between citizens, an incumbent ruler and a potential new ruler or entrant, we provide a systematic interpretation of this experience emphasizing the role of evolutionary factors such as history, uncertainty, learning and experimentation.

关于地租推进型通货膨胀的价格传导机制研究

本文认为,地租推进型通货膨胀是土地产品价格上涨推动的通货膨胀,是土地产品价值上升的结果,是土地产品价值实现的要求,不是传统意义上的通货膨胀。不同类型的货币政策下,尽管地租推进型通货膨胀的价格传导机制是不同的,其基本内容都是剩余产品在初次分配中向土地所有者的倾斜。因此,地租推进型通货膨胀的治理,核心不在于消灭地租推进型通货膨胀本身,而在于缓解收入分配带来的社会阵痛。地租推进型通货膨胀在投机资本的影响下往往呈现复合式发展的特征。地租推进型通货膨胀研究的新视角,为政府宏观调控应对土地产品价格上涨提供了全新的思路。     

Wasted waste: An evolutionary perspective on industrial by-products

Every production process gives rise to unintended outputs. We argue that whether an output is desired or undesired, is not given per se, but depends on the economic circumstances which change over time. As a result, by-products of one industry, first perceived as non-marketable wastes, may become desired inputs into other production processes. By adopting an evolutionary perspective on economic dynamics, in particular by exploiting the concept of niche exclusion, we identify favorable circumstances for undesired outputs to become marketable. To cope with the pace and unpredictability of economic evolution, we argue for a flexible policy system which favors outcome- over process-oriented waste management policies and balances the responsibility between consumers and producers on the one side, and the society as a whole on the other side.     

An evolutionary stable strategy for retailers selling complementary goods subject to indirect network externalities

A two-population evolutionary game model is constructed for retailers and used to investigate the effect of indirect network externalities (INEs) and product complementarity on the strategic choice of marketing objective of the retailers. The results show that their strategic choice of marketing objective is correlated with market reservation price (MRP) when the strength of the INE is low. When the MRP is low, the retailers tend to adopt a strategy of profit maximization. As MRP increases, low-cost retailers adopt a strategy of revenue maximization instead of profit maximization to maximize revenue at an earlier stage than high-cost retailers. However, when the strength of the INE is high, retailers only choose a strategy of revenue maximization as their marketing objective. The probability that a retailer uses a revenue maximization strategy increases as the strength of the INE grows, and product complementarity increases, when there is an equilibrium between two pure marketing objective strategies. An optimal preference ratio for retailers may exist when the strength of INE is found to be not large enough. Numerical examples reveal that the degree of preference of retailers to maximize profit is shown to be negatively correlated with both INE and product complementarity. On the other hand, their profits are positively correlated with both of these factors.     

Using pre-EMU money market rates to assess monetary policy in the euro area

This note addresses the problems arising when using national pre-EMU interest rate data in the estimation of monetary policy reaction functions for the euro area. We provide evidence that failing to adjust for interest rate risk premia leads to an overestimation of the response of monetary policy both to inflationary pressures and to the output gap. A method for adjusting pre-EMU interest rate data for risk premia is proposed.     

The relationship between exchange rates and interest rates in a small open emerging economy: The case of Romania

This paper revisits the relationship between interest rates and exchange rates in a small open emerging economy using wavelet-based methodologies. Based on data for Romania, our results confirm the theoretical predictions on the interest rate - exchange rate relationship during turmoil or policy changes. In the short term, the relationship is negative, confirming the sticky-price models, and over the long term, the relationship is positive, confirming the Purchasing Power Parity theory. At the beginning of the turmoil, the exchange rate movements generally take the lead over the interest rates for the first month, but the monetary authorities take the lead afterwards. Our results reveal that in a small open emerging economy with a direct inflation targeting monetary policy regime, the relationship between exchange rates and interest rate is fundamentally different from that in an advanced economy. Also, our results stress the necessity that the central bank must pay simultaneous attention to both variables in order to achieve their monetary policy targets.     

Equilibrium selection in bargaining models

This paper examines evolutionary equilibrium selection in bargaining models. We show that random best-response and continuous best-response learning dynamics give rise to (different) simple sufficient conditions for identifying outcomes as stochastically stable. This allows us to characterize the implications of these dynamics in simple bargaining games.     

On the geography of conventions

Summary. We study an evolutionary model in which heterogenous boundedly rational agents interact locally in order to play a coordination game. Agents differ in their mobility with mobile agents being able to relocate within a country. We find that mobile agents enjoy a higher payoff and always benefit from increased mobility, while immobile agents benefit from increased mobility at low levels of mobility only. This wedge in payoffs weakly increases as mobility increases. Some extensions are discussed. Received: January 10, 2001; revised version: December 4, 2002 RID="*" ID="*" We thank, without implicating in any way, George Mailath for helpful discussions. Some of the ideas in this paper were developed during the V Conference of the Society for the Advancement of Economic Theory in Ischia, Italy. The NSF provided financial support. Correspondence to: T. Temzelides