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Hello, We recently published a model in the Journal of Economic Behavior and Organization which addresses some of the issues raised in this thread. The model is an agent-based model in which the agent's rules are evolved using evolutionary computation, i.e., the agent learns by experience. Agents form groups which show modified power law aspects; there are clear benefits to group formation but the upper size of groups is constrained by the ability to maintain communications with ever larger numbers of individuals. The size of groups is determined largely by the relative opportunity costs of individual search and observation of other agents. Low costs lead to larger groups whose members communicate infrequently; high costs lead to small groups with intense interactions. Wilson, et al. Costly information and the evolution of self-organization in a small, complex economy. Journal of Economic Behavior & Organization 90S (2013) S76–S93 Jim Wilson Professor of Marine Sciences and Economics School of Marine Sciences University of Maine 207-581-4368 (office) 207-991-4368 (cell) On Sep 26, 2013, at 4:27 AM, Jose Javier Ramasco <[log in to unmask]> wrote: > Hello, > > power-laws or, more generically, wide distributions of group sizes can be present in many social systems. However, assuming a direct proportional agglomeration in the dynamics of the model may fall short to describe all the characteristics of the group evolution. Here there is a model in which heterogeneity is added to a Simon-like "richer-get-richer" dynamics to explain the variability of growth rates for the social groups in Flickr: > > Przemyslaw A. Grabowicz, Victor M. Eguiluz > Heterogeneity shapes groups growth in social online communities > EPL 97 28002, 2012, > > Best, > > Jose > > -- > -------------------------------------------------------------- > Jose Javier Ramasco email: [log in to unmask] > IFISC (CSIC-UIB), http://ifisc.uib-csic.es/jramasco > Edifici Inst. Univ. Recerca, > Campus Univ. Illes Balears, fax: ++ (34) 971 173 248 > 07122 Palma de Mallorca, Spain. phone: ++ (34) 971 259 886 > --------------------------------------------------------------