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Agent-based models (ABMs) provide a methodology to explore systems of interacting, adaptive, diverse, spatially situated actors. Outcomes in ABMs can be equilibrium points, equilibrium distributions, cycles, randomness, or complex patterns; these outcomes are not directly determined by assumptions but instead emerge from the interactions of actors in the model. These behaviors may range from rational and payoff-maximizing strategies to rules that mimic heuristics identified by cognitive science. Agent-based techniques can be applied in isolation to create high-fidelity models and to explore new questions using simple constructions. They can also be used as a complement to deductive techniques. Overall, ABMs offer the potential to advance social sciences and to help us better understand our complex world.

Agent-based models (ABMs) provide a methodology to explore systems of interacting, adaptive, diverse, spatially situated actors. Outcomes in ABMs can be equilibrium points, equilibrium distributions, cycles, randomness, or complex patterns; these outcomes are not directly determined by assumptions but instead emerge from the interactions of actors in the model. These behaviors may range from rational and payoff-maximizing strategies to rules that mimic heuristics identified by cognitive science. Agent-based techniques can be applied in isolation to create high-fidelity models and to explore new questions using simple constructions. They can also be used as a complement to deductive techniques. Overall, ABMs offer the potential to advance social sciences and to help us better understand our complex world. Adapted from the source document.

Doutoramento em Economia ; A crise financeira de 2007/2008 desencadeou uma onda de críticas à teoria económica. Ataques baseados em quatro críticas principais: os economistas não terem previsto a maior crise desde a Grande Depressão; as autoridades deixarem formar bolhas sem controlo; o falhanço da supervisão bancária; e os modelos usados serem desfasados da realidade. No caso dos modelos, o alvo principal são os modelos DSGE (dinâmicos, estocásticos e de equilíbrio geral) e duas das suas hipóteses simplificadoras: o agente representativo e a racionalidade. As economias são realidades complexas, não-lineares e heterogéneas, e o recurso a métodos computacionais pode ser uma alternativa para ultrapassar as limitações dos modelos tradicionais. O objectivo desta tese é alargar a aplicação dos modelos de agentes em Macroeconomia com três exemplos distintos. O primeiro é um modelo de crescimento endógeno, de gerações sobrepostas, em que a decisão dos agentes sobre estudar é baseada na satisfação e na influência dos seus pares. É usado para testar os efeitos de longo prazo do paradoxo de Easterlin, que sugere que a satisfação e o rendimento não têm uma relação linear. Verifica-se que, no cenário de Easterlin, o crescimento é menor do que no cenário base onde os agentes atribuem igual importância ao rendimento absoluto e relativo. O segundo modelo visa avaliar o contágio dos defaults da dívida pública e a forma como as estratégias dos governos afetam o seu aparecimento e propagação. As simulações mostram que os países mais gastadores e com menor aversão ao risco tendem a entrar mais vezes em default e que políticas monetárias muito expansionistas podem originar fenómenos de risco moral. No terceiro modelo, estudamos o fenómeno da 'fuga de cérebros' e as consequências no crescimento económico. Concluímos que o efeito positivo do brain drain na acumulação de capital humano depende fortemente da probabilidade de emigrar. ; The 2007/2008 financial crisis triggered a wave of criticism of the economic theory. These attacks are based in four main critics: economists had not foreseen the biggest crisis since the Great Depression; authorities let bubbles form without control; weak banking supervision; and the models used in macroeconomic policy being out of touch with reality. In the particular case of the macroeconomic models, the target are the DSGE models (dynamic, stochastic and general equilibrium) and their two simplifying hypotheses: the representative agent and rationality. Economies are complex realities, with nonlinearities and heterogeneities, and computational economics can be an advantageous alternative to overcome the shortcomings of the traditional models. The aim of this thesis is to extend the application of agent-based models to macroeconomic topics in three distinct models. The first one is an endogenous growth model, in an overlapping generations environment, in which the agents' individual decision to study is based on the satisfaction of their peers. It is used to evaluate the long-term effects of the Easterlin paradox, which states that satisfaction and income have a non-linear relation. The second model is used to study sovereign default contagion in order to assess how different government strategies affect default and propagation across countries. Simulations showed that high spending and low risk aversion levels are associated to a high prevalence of default and that monetary stimulus can create moral hazard problems. In the third model, we study the brain drain phenomenon and its economic growth effects. We conclude that beneficial brain hypothesis depend heavily on emigration probability. ; info:eu-repo/semantics/publishedVersion

The primary goal of this book is to present the research findings and conclusions of physicists, economists, mathematicians and financial engineers working in the field of "Econophysics" who have undertaken agent-based modelling, comparison with empirical studies and related investigations. Most standard economic models assume the existence of the representative agent, who is "perfectly rational" and applies the utility maximization principle when taking action. One reason for this is the desire to keep models mathematically tractable: no tools are available to economists for solving non-linear models of heterogeneous adaptive agents without explicit optimization. In contrast, multi-agent models, which originated from statistical physics considerations, allow us to go beyond the prototype theories of traditional economics involving the representative agent. This book is based on the Econophys-Kolkata VII Workshop, at which many such modelling efforts were presented. In the book, leading researchers in their fields report on their latest work, consider recent developments and review the contemporary literature

Occurrences of crime are complex phenomena. They are the result of a large number of interrelated elements which can include environmental factors as well as complex human behaviours. Traditionally, crime occurrences have been modelled using statistical techniques, and although such approaches are useful, they face difficulties in providing predictive analyses and with the integration of behavioural information. Also, it is particularly difficult to account for the strongly influential effect of local urban form. Agent-based modelling is a relatively new modelling paradigm that has generated a considerable amount of interest. An agent is an independent component of a system which interacts with other agents and its environment to achieve goals. In this manner, large systems of agents can be created to mimic real scenarios. Most importantly, the agents can incorporate behavioural information to determine how they should achieve their goals, and models can include a highly detailed environment. This paper presents an agent-based model used to predict burglary rates, which, despite its simplicity, yields interesting results. We apply the model to the city of Leeds, UK. The model indicates that the urban configuration in Leeds is a major element in determining the level of crime across the city. It also demonstrates that agent-based modelling is an excellent tool for these types of analyses with much potential.

Party competition for votes in free and fair elections involves complex interactions by multiple actors in political landscapes that are continuously evolving, yet classical theoretical approaches to the subject leave many important questions unanswered. Here Michael Laver and Ernest Sergenti offer the first comprehensive treatment of party competition using the computational techniques of agent-based modeling. This exciting new technology enables researchers to model competition between several different political parties for the support of voters with widely varying preferences on many different issues.

An organization is a collection of agents that interact and produce some form of output. Formal organizations - such as corporations and governments - are typically constructed for an explicit purpose though this purpose needn't be shared by all organizational members. An entrepreneur who creates a firm may do so in order to generate personal wealth but the worker she hires may have very different goals. As opposed to more amorphous collections of agents such as friendship networks and societies at large, organizations have a formal structure to them (though informal structures typically emerge as well) with the prototypical example being a corporation's organizational chart. This structure serves to define lines of communication and the distribution of decision-making. Organizations are also distinguished by their well-defined boundaries as reflected in a clear delineation as to who is and who is not a member. This boundary serves to make organizations a natural unit of selection; for example, corporations are formed and liquidated though they can also morph into something different through activities like mergers.

Party competition for votes in free and fair elections involves complex interactions by multiple actors in political landscapes that are continuously evolving, yet classical theoretical approaches to the subject leave many important questions unanswered. Here Michael Laver and Ernest Sergenti offer the first comprehensive treatment of party competition using the computational techniques of agent-based modeling. This exciting new technology enables researchers to model competition between several different political parties for the support of voters with widely varying preferences on many diff