Monday, January 19, 2009

Generations Model

The Schelling (1971, 1978) model of segregation is probably one of the best known agent-based models and unknowingly, one of the pioneers in the field of Aagent-based modelling (Schelling, 2006). He emphasised the value of starting with rules of behaviour for individuals and using simulation to discover the implications for large scale aggregate outcomes through the interactions of these individuals. This key feature of the model arises because the decisions of any one individual can impact in unexpected and unanticipated ways upon the decisions of others.

While the model is excellent in the sense that it uses of simple logic to illustrate how segregation could emerge, through the mild tastes and preferences to locate amongst like social or economic groups. The model has no population turnover (Fossett and Waren, 2005), households are ‘immortal’ and thus a satisfied household can reside in the same location for ever.

While I been exploring Schellings model (see Crooks, 2008), recently I cam across the "Generations Model" by Hugh Stimson which extends Schellings model so that agents have a chance of of dying and giving birth. But what is interesting about the model is that depending on how many agents of opposite type live nearby, agents may give birth to a new 'mixed' type of agent, who do not share their parent’s biases.

The model is programmed in RepastJ and can be downloaded from here (30kb). More information about the model can be found on Hugh Stimson's blog.


Crooks, A. T. (2008), Constructing and Implementing an Agent-Based Model of Residential Segregation through Vector GIS, Centre for Advanced Spatial Analysis (University College London): Working Paper 133, London, England. (pdf)

Fossett, M. and Waren, W. (2005), Overlooked Implications of Ethnic Preferences for Residential Segregation in Agent-Based Models, Urban Studies, 42(11): 1893-1917.

Schelling, T.C. (1971), Dynamic Models of Segregation, Journal of Mathematical Sociology 1: 143-186.

Schelling, T.C. (1978), Micromotives and Macrobehavior, WW Norton and Company, New York, NY.

Schelling, T.C. (2006), Some Fun, Thirty-Five Years Ago, in Tesfatsion, L. and Judd, K.L. (eds.), Handbook of Computational Economics: Agent-Based Computational Economics, North-Holland Publishing, Amsterdam, Netherlands, pp. 1639-1644.

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