We create a dynamic theory of endogenous risk sharing groups, with good internal information, and their coexistence with relative performance, individualistic regimes, which are informationally more opaque. Inequality and organizational form are determined simultaneously. Numerical techniques and succinct re-formulations of mechanism design problems with suitable choice of promised utilities al...

Is it possible, simply by asking a few members of a community, to identify individuals who are best placed to diffuse information? A model of diffusion shows how members of a community can, just by tracking gossip about others, identify those who are most central in a network according to “diffusion centrality” – a network centrality measure that predicts the diffusion of a piece of information...

This paper studies bilateral insurance schemes across networks of individuals. While transfers are based on social norms, each individual must have the incentive to abide by those norms, and so we investigate the structure of self-enforcing insurance networks. Network links play two distinct and possibly conflictual roles. First, they act as conduits for transfers. Second, they act as conduits ...

The “friendship paradox” (Feld (1991)) refers to the fact that, on average, people have strictly fewer friends than their friends have. I show that this over-sampling of the most popular people amplifies behaviors that involve complementarities. People with more friends experience greater complementarities and hence take more extreme actions. Given the friendship paradox, people then perceive m...

The paper concerns a dynamic model of influence in which agents make a yes-no decision. Each agent has an initial opinion which he may change during different phases of interaction, due to mutual influence among agents. We investigate a model of influence based on aggregation functions. Each agent modifies his opinion independently of the others, by aggregating the current opinion of all agents...

We consider a model of influence with a set of non-strategic agents and two strategic agents. The non-strategic agents have initial opinions and are linked through a simply connected network. They update their opinions as in the DeGroot model. The two strategic agents have fixed and opposed opinions. They each form a link with a non-strategic agent in order to influence the average opinion that...

Ostrovsky (2008) [9] develops a theory of stability for a model of matching in exogenously given networks. For this model a generalization of pairwise stability, chain stability, can always be satisfied as long as agents’ preferences satisfy same side substitutability and cross side complementarity. Given this preference domain I analyze the interplay between properties of the network structure...

This paper models the dynamic process through which a large society may succeed in building up its ‘social capital’, i.e. a stable and dense pattern of interaction among its members. Agents play repeatedly an idiosyncratic Prisoner’s Dilemma with their neighbors. The social network specifies not only the playing partners but, crucially, also determines how relevant strategic information diffuse...

We present a dynamic model of network formation where nodes find other nodes with whom to form links in two ways: some are found uniformly at random, while others are found by searching locally through the current structure of the network (e.g., meeting friends of friends). This combination of meeting processes results in a spectrum of features exhibited by large social networks, including the ...

urbanization agglomeration that is named jacobs externalities, refers to the role of economic diversification in urban. localization agglomeration, marshal-arrow-romer (mar) externalities, is related to the concentration of firms activated in a special industry within a specified place. the purpose of this research is to explore the impact of different types of agglomeration economies on employ...