Simulating Evolutionary Games: A Python-Based Introduction

This paper is an introduction to agent-based simulation using the Python programming language. The core objective of the paper is to enable students, teachers, and researchers immediately to begin social-science simulation projects in a general purpose programming language. This objective is facilitated by design features of the Python programming language, which we very briefly discuss. The paper has a 'tutorial' component, in that it is enablement-focused and therefore strongly application-oriented. As our illustrative application, we choose a classic agent-based simulation model: the evolutionary iterated prisoner's dilemma. We show how to simulate the iterated prisoner's dilemma with code that is simple and readable yet flexible and easily extensible. Despite the simplicity of the code, it constitutes a useful and easily extended simulation toolkit. We offer three examples of this extensibility: we explore the classic result that topology matters for evolutionary outcomes, we show how player type evolution is affected by payoff cardinality, and we show that strategy evaluation procedures can affect strategy persistence. Social science students and instructors should find that this paper provides adequate background to immediately begin their own simulation projects. Social science researchers will additionally be able to compare the simplicity, readability, and extensibility of the Python code with comparable simulations in other languages.Agent-Based Simulation, Python, Prisoner's Dilemma

Social Consequences of Commitment

This paper begins with a detailed computational introduction to a classic ACE model: an evolutionary prisoner's dilemma. The paper presents a simple but fully coded object oriented implementation of this model. (We use the Python programming language, which is shown to be a natural ally for ACE research). Using these tools, we demonstrate that player type evolution is affected by cardinal payoffs. We then explore a possible social benefit to commitment, where 'commitment' denotes an unwillingness to surrender a reciprocal strategy.ACE; agent-based; computational economics; iterated prisoner's dilemma; evolutionary prisoner's dilemma; commitment

The Structure of Neoclassical Consumer Theory

This paper offers an accessible introductory survey of the application of abstract choice theory to consumer theory. In the process, the paper identifires---somewhat more carefully than is usual in the literature--- the relatively small role of the rationality postulates and the relatively large role of the ad hoc assumptions that are required to produce the minimal structure of neoclassical consumer theory. (This structure is that Marshallian demand obeys the weak axiom of revealed preference in budget data). Finally, this paper serves as a reminder that economists should abandon the behaviorist aspirations and claims that they have repeatedly, but incorrectly, associated with abstract choice theory.abstract choice theory, consumer theory, neoclassical economics

The ABM Template Models -- A Reformulation with Reference Implementations

This paper refines a well-known set of template models for agent-based modeling and offers new reference implementations. It also addresses issues of design, flexibility, and ease of use that are relevant to the choice of an agent-based modeling platform.

HIV and Concurrent Sexual Partnerships: Modelling the Role of Coital Dilution

Background: The concurrency hypothesis asserts that high prevalence of overlapping sexual partnerships explains extraordinarily high HIV levels in sub-Saharan Africa. Earlier simulation models show that the network effect of concurrency can increase HIV incidence, but those models do not account for the coital dilution effect (nonprimary partnerships have lower coital frequency than primary partnerships). Methods: We modify the model of Eaton et al (AIDS and Behavior, September 2010) to incorporate coital dilution by assigning lower coital frequencies to non-primary partnerships. We parameterize coital dilution based on the empirical work of Morris et al (PLoS ONE, December 2010) and others. Following Eaton et al, we simulate the daily transmission of HIV over 250 years for 10 levels of concurrency. Results: At every level of concurrency, our focal coital-dilution simulation produces epidemic extinction. Our sensitivity analysis shows that this result is quite robust; even modestly lower coital frequencies in non-primary partnerships lead to epidemic extinction. Conclusions: In order to contribute usefully to the investigation of HIV prevalence, simulation models of concurrent partnering and HIV epidemics must incorporate realistic degrees of coital dilution. Doing so dramatically reduces the role that concurrency can play in accelerating the spread of HIV and suggests that concurrency cannot be an important driver of HIV epidemics in sub-Saharan Africa. Alternative explanations for HIV epidemics in sub- Saharan Africa are needed

The Behavioral Life-Cycle Theory Of Consumer Behavior: Survey Evidence

We find that survey evidence on faculty pay-cycle choice strongly contradicts the neoclassical theory of consumer behavior. It is more favorable to the behavioral life-cycle theory of Shefrin and Thaler (1988).behavioral life-cycle theory, consumer behavior, survey evidence

TYPOLOGY AND POLICY FOR SMALL FARMS

Agricultural and Food Policy,

The Real Interest Differential Model after Twenty Years

It has been twenty years since Frankel (1979) offered the classic empirical support for the Dornbusch (1976) overshooting model against the simple monetary approach model, and almost that long since Driskill and Sheffrin (1981) uncovered some important inconsistencies between Frankel’s theoretical framework and his empirical implementation. Frankel’s RID model nevertheless spawned a huge lit-erature in international monetary economics. In this paper, we replicate and update the Frankel (1979) and Driskill and Sheffrin (1981) results, in order to offer a retrospective and a reëvaluation of this lit-erature. We also explain why the model estimated by Driskill and Sheffrin (1981) cannot underpin a critique of Frankel (1979), a point which is not generally recognized. While specialists in international finance generally recognize that the initial promise of Frankel’s research has not been kept, we believe that many will be surprised nevertheless by our stark findings. JEL: F31, F40, C13exchange rates, real interest differential model

The Large Peculiar Velocity of the cD Galaxy in Abell 3653

We present a catalogue of galaxies in Abell 3653 from observations made with the 2dF spectrograph at the Anglo-Australian Telescope. Of the 391 objects observed, we find 111 are bone-fide members of Abell 3653. We show that the cluster has a velocity of cz = 32214 +/- 83 km/s (z=0.10738 +/- 0.00027), with a velocity dispersion typical of rich, massive clusters of sigma_{cz} = 880^{+66}_{-54}. We find that the cD galaxy has a peculiar velocity of 683 +/- 96 km/s in the cluster restframe - some 7sigma away from the mean cluster velocity, making it one of the largest and most significant peculiar velocities found for a cD galaxy to date. We investigate the cluster for signs of substructure, but do not find any significant groupings on any length scale. We consider the implications of our findings on cD formation theories.Comment: 16 pages, including 7 figures and a long table. Accepted for publication in MNRA