2 My definition of institutions as mechanisms to provide individuals with reputational information on potential interaction partners is deliberately narrow in this paper.

3 The simulations reported in the paper were run on MATLAB. Please contact the author for the program code.

4 An alternative method is to model state-led assimilation which would differ from the strictly local interaction topology modeled here. The state could be modeled as a distinct cultural string communicating with "villages" within its territory, thereby introducing tension between the decentralized mechanism for cultural change specified here and a central actor.

5 Population estimates from the 13 th Century are available for a number of major cities, although these cities do not account for each of the contemporary regions of Italy.

6 Putnam does not include Sardegna in his depiction of 14 th Century Italy. As a result, I left Sardegna out of the model.

7 I note at the outset that the boot-shaped landscape introduces some peculiarity into the simulation, particularly in the form of boundary effects.

8 To measure civicness, Putnam assesses the vibrancy of associational life, the incidence of newspaper readership across the Italian regions, regional differences in turnout in successive public referenda, and the incidence of preference voting (which reflects clientalistic obligations).

9 One can therefore think of agents as individuals in established territorial domains or "villages," to borrow a term used by Axelrod (1997: 99) in his model of social influence. Mobile agents can be introduced in the model, although this remains a task for future research.

10 Agent i may have a maximum of eight neighbors, although if i was to be located on an edge or a region's boundary she may have fewer than eight neighbors. I later relax this condition, and permit agents to interact across political boundaries although the edge effects remain.

11 This assumes that the least effective institutions have the greatest room for improvement.

12 I assume that the effect of interaction is one-sided to avoid forced cultural change, that is change imposed by a on b. The assumption can be relaxed in future versions of the model.