We investigate the origins of identity and the innate proclivity to draw a distinction between `insiders' and `outsiders'. We propose an evolutionary explanation: we argue that identity arises because it facilitates survival. In an evolutionary setting we endogenize preferences and demonstrate...

We analyze the success of filtering as a solution to the spam problem when used alone or concurrently with sender pricing, receiver pricing, or both. We find that filtering alone may exacerbate the spam problem in terms of both the total number of spam message sent and the expected number of...

A social dilemma is, in essence, a prisoners' dilemma in a continuous strategy space. I discuss a number of social dilemmas that have caught my attention, offer an elementary, diagrammatic synthesis of them, and discuss some of the economic insights that the diagrams capture, including...

We provide a model of know-how sharing between competing firms in which each of two firms gets a stochastic innovation in its stock of know-how in every period. Separately considering the cases when innovations are indivisible and divisible, we examine the nature of the subgame perfect sharing...