基于主体的计算经济学

基于主体的计算经济学 Agent-based Computational Economics (ACE)计算经济学的一个研究领域,将整个经济视作不同主体相互作用的动态系统,研究经济的发展过程。[1][2] 因此,它属于复杂适应系统的科学范式。在相应的基于主体模型中,“主体”指根据特定规则进行交互的计算实体,而非真实的人。其中交互的规则一种对个体行为和社会互动的建模。[3] 这些规则甚至可以通过人工智能方法(如Q学习 Q-learning及其他强化学习技术)来获得。[4]


传统经济学中个体会理性地计算均衡状态地理论假设被舍弃,取而代之地是更为宽松、现实地假设——个体的理性有限,且其行为仅仅是对市场变化做出适应(而非计算均衡)。[5][6][7]基于主体的计算经济学模型(ACE)将数值分析方法应用于复杂动力学问题,进行计算机模拟,这种方法可以应对传统方法,如数学方程不适用的问题。[8]\从建模者指定的初始条件开始,计算经济学模型会随着时间的推移而不断演化,模型中的主体不断地对其他参与者交互,包括从交互中学习。在这个角度来看,ACE 被认为是一种自下而上研究经济系统的方法。[9]


ACE 与博弈论时有相似之处和重叠部分,都可以看作以一种研究社会交往的基于主体的建模方法。[10][11][12] 但实践者也注意到了ACE与标准的博弈论方法的区别,例如,在ACE中,事件仅由初始条件驱动;ACE不在乎计算上是否易于处理;ACE中,主体有自动选择和学习的能力。[13]


得益于计算机科学建模技术的不断改进和计算机能力的提高,ACE方法也在不断发展,其终极科学目标是“用实际数据来检验理论发现——使得可靠的、有实际经验和数据支撑的理论能不断积累,而研究人员也能在可靠的前人理论基础上做进一步探索。”[14][15][16]现在,ACE方法已应用于如资产定价、[17]竞争与合作、[18] 交易成本 Transaction Cost[19]市场形式与产业组织 Industrial Organization与动态、[20][21]福利经济学 Welfare Economics[22] 机制设计 Mechanism Design[23][24][25][26][27][28]信息与不确定性、[29] 宏观经济学 Macroeconomics[30][31][32]马克思主义政治经济学 Marxist economics[33][34]等研究领域。


概述

ACE 模型中的“主体(agent)”可以代表个体(如人)、社会群体(如公司)、生物实体(如生长中的庄稼)和/或物理系统(如运输系统),整个ACE模型就是由多个相互作用的主体组成的计算经济系统。建模者首先为ACE模型设置初始参数。然后,ACE模型就会自行演化,建模人员则观察系统随着时间的推移而演化的情况,不需要做进一步的干预。注意,系统活动应由主体间的相互作用驱动,而不需要外部强加平衡条件。[35]目前来说,ACE面临的研究问题包括所有实验经济学 Experimental economics会遇到的普遍问题,[36]以及开发用于验证模型正确性的的通用框架,和其他基于主体的建模中尚未解决的开放问题。[37]


ACE 同时也是是美国计算经济学学会的一个官方特殊兴趣团体 special interest group (SIG)。圣塔菲研究所_Santa_Fe_Institute的研究人员为 ACE 的发展做出了贡献。


举例:金融

ACE 方法已广泛应用的领域之一是资产定价。布莱恩·亚瑟 W. Brian Arthur、埃里克·鲍姆 Eric Baum、威廉·布洛克 William Brock、卡森·帕尔默 Cars Hommes和布莱克·勒巴朗 Blake LeBaron等人已开发出一个计算模型,其中许多主体从一组可能的预测策略中选择一种或几种以预测股票价格,他们自己的预测结果影响了他们的自己的资产需求,进而影响整体股票价格。这些模型假设每个主体更有可能选择最近前几轮中成功的预测策略。任何策略的成功取决于市场条件,也取决于目前正在被主体们使用的预测策略。这些模型的实验结果经常表明,随着主体改换预测策略,资产价格可能会出现大起大落。[17][38][39]最近,Brock、Hommes和 Wagener 使用了这类模型来论证引入新的对冲工具可能会破坏市场稳定,[40] 一些论文提出,ACE 可能是理解最近金融危机 financial crisis的有用方法。[41][42][43]


参见


参考文献

  1. W. Brian Arthur, 1994. "Inductive Reasoning and Bounded Rationality," American Economic Review, 84(2), pp. 406-411.
  2. Leigh Tesfatsion, 2003. "Agent-based Computational Economics: Modeling Economies as Complex Adaptive Systems," Information Sciences, 149(4), pp. 262-268.
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  8. Kenneth L. Judd, 2006. "Computationally Intensive Analyses in Economics," Handbook of Computational Economics, v. 2, ch. 17, Introduction, p. 883. [Pp. 881- 893. Pre-pub PDF.
  9. Leigh Tesfatsion (2002). "Agent-Based Computational Economics: Growing Economies from the Bottom Up," Artificial Life, 8(1), pp.55-82. Abstract and pre-pub PDF
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  14. Leigh Tesfatsion (2006). "Agent-Based Computational Economics: A Constructive Approach to Economic Theory," ch. 16, Handbook of Computational Economics, v. 2, [pp. 831-880] sect. 5. Abstract and pre-pub PDF.
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  19. Tomas B. Klosa and Bart Nooteboom, 2001. "Agent-based Computational Transaction Cost Economics," Journal of Economic Dynamics and Control 25(3–4), pp. 503–52. Abstract.
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  40. Brock, W.; Hommes, C.; Wagener, F. (2009). "More hedging instruments may destabilize markets" (PDF). Journal of Economic Dynamics and Control. 33 (11): 1912–1928. doi:10.1016/j.jedc.2009.05.004.
  41. M. Buchanan (2009), 'Meltdown modelling. Could agent-based computer models prevent another financial crisis?.' Nature, Vol. 460, No. 7256. (5 August 2009), pp. 680-682.
  42. J.D. Farmer, D. Foley (2009), 'The economy needs agent-based modelling.' Nature, Vol. 460, No. 7256. (5 August 2009), pp. 685-686.
  43. M. Holcombe, S. Coakley, M.Kiran, S. Chin, C. Greenough, D.Worth, S.Cincotti, M.Raberto, A. Teglio, C. Deissenberg, S. van der Hoog, H. Dawid, S. Gemkow, P. Harting, M. Neugart. Large-scale Modeling of Economic Systems, Complex Systems, 22(2), 175-191, 2013


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