On economic applications of the genetic algorithm: a model of the cobweb type

This paper explores the idea of using artificial adaptive agents in economic theory. In particular, we use Genetic Algorithms (GAs) to model the learning behavior of a population of adaptive and boundedly rational agents interacting in an economic system. We analyze the behavior of a GA in two versions of a model of the cobweb-type, one in which firms make only quantity choices, and the other one in which firms first decide to exit or to stay in the market, and subsequently decide how much to produce. We present simulations with different coding schemes and interpret the rather surprising differences between the results for different setups by employing the mathematical theory for GAs with state-dependent fitness functions. In particular, we explain the relationship between coding and convergence properties of GAs.     

Unstable and stable steady-states in the Kiyotaki-Wright model

Summary. I provide new results concerning dynamics for a version of the Kiyotaki-Wright model (1989) in which strategies (either mixed or pure) are restricted so that agents play the same strategy for each opportunity set. My results demonstrate the importance of examining stability in such models, because they show that many steady states focused on in the literature are not stable. Furthermore, I exhibit examples of two-period-convergent equilibria in which agents are indifferent among media of exchange. Consequently, their endogenous transaction pattern is analog to the coexistence of assets whose acceptability or “liquidity” varies inversely with their rates of return. Received: June 21, 1996; revised version: December 2, 1996     

关于后金融危机时代粮价上涨的思考

金融危机时代,粮价飞涨,后金融危机时代,粮价依然居高不下,前者能用传统发散型蛛网模型理论解释,但后者却无法用传统理论分析。在市场自身机制调节外,非市场因素也会对粮价波动造成较大的影响,鉴于此,应该加强流动性监管以有效平抑粮价,提高农民种粮收益,鼓励种粮,多项举措促使农民卖粮,促进粮食市场的健康发展。     

Using co-evolutionary programming to simulate strategic behaviour in markets

This paper describes the use of a genetic algorithm (GA) to model several standard industrial organisation games: Bertrand and Cournot competition, a vertical chain of monopolies, and a simple model of an electricity pool. The intention is to demonstrate that the GA performs well as a modelling tool in these standard settings, and that evolutionary programming therefore has a potential role in applied work requiring detailed market simulation. The advantages of using a GA over scenario analysis for applied market simulation are outlined. Also explored are the way in which the equilibria discovered by the GA can be interpreted, and what the market analogue for the GA process might be.     

Learning and behavioral stability An economic interpretation of genetic algorithms

This article tries to connect two separate strands of literature concerning genetic algorithms. On the one hand, extensive research took place in mathematics and closely related sciences in order to find out more about the properties of genetic algorithms as stochastic processes. On the other hand, recent economic literature uses genetic algorithms as a metaphor for social learning. This paper will face the question of what an economist can learn from the mathematical branch of research, especially concerning the convergence and stability properties of the genetic algorithm. It is shown that genetic algorithm learning is a compound of three different learning schemes. First, each particular scheme is analyzed. Then it is shown that it is the combination of the three schemes that gives genetic algorithm learning its special flair: A kind of stability somewhere in between asymptotic convergence and explosion.     

The behavior of the exchange rate in the genetic algorithm with agents having long memory

This paper studies the behavior of the exchange rate in Kareken and Wallace (1981)'s model under the genetic algorithm adaptation with agents having long memory. The simulation results show that, if agents have full memory, the average portfolio fraction will converge, and the initial equilibrium that it converges to is history dependent. Under the lasting evolutionary pressure of the noise trader, the market will eventually drift from one equilibrium to another, and asymptotically will converge to the neighborhood of an equilibrium with agents putting their savings equally into two currencies. If the agents do not have full memory, the foreign exchange market will show periodic crisis. Before and after a market crises, the average portfolio fraction will converge to different stationary equilibria. A mean difference equation of the average portfolio fraction is also given to describe the dynamics of the model.

On the dynamics of an endogenous growth model with learning by doing

Summary. The paper studies the local dynamics of an endogenous growth model with externalities of investment. It is demonstrated that, in case of sustained per capita growth, the competitve economy is characterized by a situation with a unique balanced growth path which is saddle point stable or by a situation with two balanced growth paths. If there are two balanced growth paths, the one with the higher growth rate is a saddle point whereas the path with the lower growth rate is either completely stable, with convergence to a rest point or limit cycle, or completely unstable. In the social optimum the existence of a balanced growth path implies that it is unique and that this path is a saddle point. Received: May 15, 2000; revised version: December 14, 2001     

Interdependency and adjustments in the European Union

Since the euro was launched, divergences in European economies'evolutions have been more significant than generally expected. The article, based on a multinational macroeconomic model describing the interdependence between 14 European countries, examines the role played by relative‐price adjustment mechanisms and difficulties inherent in asymmetric evolutions.

The efficiency of relative‐price adjustment mechanisms seems limited and, even in the most flexible countries, the return to equilibrium is slow and still incomplete after 10 years. Differences in relative‐price adjustment mechanisms remain a source of asymmetries between member countries. Extra‐European exchanges have a stabilizing role which is uneven on account of trade openness and price elasticities. A decrease of the world demand and a depreciation of the euro, still have an important impact with significant disparities between countries.

Several lessons can be drawn in terms of economic policy. A more restrictive European fiscal policy proves more costly in the long run in Germany and the Netherlands on account of the weakness of price compensation effects. On the contrary, thanks to their greater flexibility, the United Kingdom and Sweden can offset an initial negative shock more rapidly. The wage dimension in the definition of a good European policy mix has also to be examined.     

Modification of Costanza's model of valuing ecosystem services and its application in China

In the past, evaluations of ecosystem functions were mostly based on Costanza's model, whereas the spatial, quality and temporal characteristics of regional ecosystems were not considered in the model.Focusing on these Issues, coefficients of regional difference, spatial heterogeneity and willingness-to-pay (WTP) were established to modify Costanza's model, and a new comprehensive valuation model of ecosystem functions is proposed.The analytical results indicate that the comprehensive model could evaluate regional ecosystem functions in China accurately and provide more helpful information for decision-making.The empirical study on Zhangbei County in Hebei Province shows that the intensive human activities could limit the provision of ecosystem functions while the planned ecological programs might promote the restoration of ecosystem functions.     

Elasticity of substitution and growth: normalized CES in the Diamond model

Summary. It is often asserted that the more substitutable capital and labor are in the aggregate production the more rapidly an economy grows. Recently this has been formally confirmed within the Solow model by Klump and de La Grandville (2000). This paper demonstrates that there exists no such monotonic relationship between factor substitutability and growth in the Diamond overlapping-generations model. In particular, we prove that, if capital and labor are relatively substitutable, a country with a greater elasticity of substitution exhibits lower per capita output growth in transit and in steady state. Received: October 27, 2001; revised version: February 25, 2002     

创新型大企业的星云模型与选择子企业的遗传算法研究

通过分析创新型大企业的创新内涵和规模外延,建立了星云模型,针对构建中选择子企业的实际需要,提出改进的遗传算法,引入倒位算子代替交叉操作,建立了企业间协同系数矩阵和相应的适应度函数,提高了对此类多目标组合优化问题求解的有效性。     

Aggregate demand,sunk costs and discontinuous adjustments in an amended new consensus model

In standard new consensus macroeconomics models, the impact of shocks disappears until the economy reaches a time-independent steady-state equilibrium. Introducing sunk costs and capital indivisibilities in capacity adjustment decisions implies the rejection of asymptotic stability and a reconsideration of the relevance and usefulness of traditional steady-state analysis based on a fixed and exogenous ‘center of gravity’. Moreover, effective demand and Keynesian discretionary policies regain a central role in economic policy by determining the transient equilibriums that emerge endogenously.     

Seasonality and Markov switching in an unobserved component time series model

It is generally acknowledged that the growth rate of output, the seasonal pattern, and the business cycle are best estimated simultaneously. To achieve this, we develop an unobserved component time series model for seasonally unadjusted US GDP. Our model incorporates a Markov switching regime to produce periods of expansion and recession, both of which are characterized by different underlying growth rates. Although both growth rates are time-varying, they are assumed to be cointegrated. The analysis is Bayesian, which fully accounts for all sources of uncertainty. Comparison with results from a similar model for seasonally adjusted data indicates that the seasonal adjustment of the data significantly alters several aspects of the full model. First Version Received: January 2001/Final Version Received: February 2002 Send offprint requests to: Rob Luginbuhl?Correspondence to: Rob Luginbuhl     

Service innovation and the proximity-concentration trade-off model of trade and FDI

This paper introduces service innovation in the proximity-concentration trade-off model of trade and foreign direct investments (FDI) [Helpman, E., M. Melitz, and S. R. Yeaple 2004 Helpman, E., M. Melitz, and S. R. Yeaple. 2004. “Export Versus FDI with Heterogeneous Firms.” American Economic Review 94 (1): 300–316. doi: 10.1257/000282804322970814[Crossref], [Web of Science ®] , [Google Scholar]. “Export Versus FDI with Heterogeneous Firms.” American Economic Review 94 (1): 300–316]. The idea is that innovation will have two main effects on service firms’ choice between exports and FDI. First, innovative firms will on average have higher productivity levels than non-innovative enterprises. Secondly, innovators will have to pay a higher relational distance cost for undertaking export activities, and they will, therefore, prefer to avoid (or reduce) these costs by choosing an FDI strategy instead. We test the empirical relevance of this idea on a new survey data set for a representative sample of firms in all business service sectors in Norway. The results show that firms are more likely to choose FDI rather than export the greater their productivity level and the higher the relational distance costs they face.     

Reassessing the empirical validity of the human-capital augmented neoclassical growth model

We reassess Mankiw, Romer and Weil's [mrw] version of the Solow model using, as did mrw, cross-sectional data to estimate the steady-state equation governing income per capita levels. The model fails in two critical areas. First, plausible factor shares obtained by mrw are not robust to the substitution of two measures of human capital that are more precise than the secondary school enrollment rates used by mrw. Second, the null hypothesis of an exogenous and identical level of technology in all countries is rejected. We also explain why the Solow model performed well despite the above shortcomings.     

环境规制对碳效率的多重路径及门槛模型研究

从结构升级及效率提升两大维度刻画环境规制对碳排放效率的关系及作用机制,研究环境规制是如何提升城市碳排放效率的。基于2006—2019年中国279个城市层面数据,采用非参数百分位自抽法,逐步回归法、Sobel检验和交互调节模型验证影响路径,并利用门槛模型探讨不同路径下环境规制的调节作用。结果表明：(1)环境规制促进城市碳排放效率提升,但存在区域异质性;(2)环境规制通过促进产业结构高度化、绿色技术创新和能源效率升级提高碳排放效率,产业结构合理化及产业集聚“遮掩”了环境规制的激励作用;(3)环境规制对提升碳排放效率存在多种门槛效应和调节机制。发挥环境规制对碳排放效率结构和效率的双重激励时,需注意不同路径的维度问题,以提高准度,把握力度。     

Price and quantity adjustments in the Austrian labour market

Austria is among the very few countries in the European Union which have managed to maintain comparatively low unemployment rates and high employment rates. This study looks at the price and quantity adjustment mechanisms in the Austrian labour market which may have contributed to this favourable outcome. After reviewing briefly the basic theoretical reasoning an empirical investigation is began into gross flow dynamics in the labour market and the cyclical volatility of employment and unemployment in Austria. In international comparison Austrian unemployment is very stable over the business cycle. This is due mainly to the high sensitivity of the labour force on cyclical conditions and, partly, also on the relatively weak responsiveness of employment to cyclical fluctuations in output, the latter being possibly attributable to the high degree of real wage flexibility in Austria. The study proceeds to show that the long-run elasticity of wages with respect to unemployment is indeed quite high in Austria. However, evidence was also found for outsider effects in the Austrian wage setting process. Relative wage structures, on the other hand, appear to be rather rigid.     

The dynamics of firms in a micro-to-macro model: The role of training, learning and innovation

We analyze the co-evolution of the performances of firms and of the economy in an evolutionary micro-to-macro model of the Swedish economy. The model emphasizes the interactions between human capital (or competences) and technological change at the firm level and their effects on aggregate growth, taking into account the micro-macro feedbacks. The model features learning-by-doing, incremental and radical innovations, user-producer learning at the firm level, and a change in the techno-economic paradigm. We find that there is an optimal sequence for the firm to allocate their resources: (1) build a general human capital stock before the change in the techno-economic paradigm, (2) spend on R&D, and (3) invest in specific human capital. Innovators fare better than imitators on average, not only because they innovate, but also because they build a competence base, which supports the learning from other firms.     

A modified logit model for time series with an application to the pricing behaviour of manufacturing firms in Australia

The modified logit model (Amemiya and Nold, 1975) is generalised to the case where the error term is autocorrelated. The asymptotic distribution (as n →∞ and T →∞) of a feasible GLS estimator of β is derived. Tests of linear restrictions on β and the significance of ρ are presented. The results of the applied work suggest that the factors which explain the pricing behaviour of manufacturing firms, as reported in the tendency survey conducted by the Australian Chamber of Commerce and Industry and the Westpac Banking Corporation, include historical inflation rates of up to 7 quarters and capacity utilisation. First version received: March 2001/Final version received: July 2002 RID="*" ID="*"  The first draft of this paper was written while the author was on study leave at the Department of Econometrics, University of Sydney, Australia.     

Evolutionary economics goes mainstream: A review of the theory of learning in games

The Theory of Learning in Games by Fudenberg and Levine surveys a key branch of evolutionary economics from a mainstream perspective. Its publication provides an opportunity to reassess the prospects and goals for evolutionary economics.