This article develops an elementary theory of global supply chains. We consider a world economy with an arbitrary number of countries, one factor of production, a continuum of intermediate goods and one final good. Production of the final good is sequential and subject to mistakes. In the unique free trade equilibrium, countries with lower probabilities of making mistakes at all stages specialize in later stages of production. Using this simple theoretical framework, we offer a first look at how vertical specialization shapes the interdependence of nations. Copyright , Oxford University Press.

We study stochastic games with an infinite horizon and sequential moves played by an arbitrary number of players. We assume that social memory is finite--every player, except possibly one, is finitely lived and cannot observe events that are sufficiently far back in the past. This class of games includes games between a long-run player and a sequence of short-run players, and games with overlapping generations of players. An equilibrium is purifiable if some close-by behaviour is consistent with equilibrium when agents' payoffs in each period are perturbed additively and independently. We show that only Markov equilibria are purifiable when social memory is finite. Thus if a game has at most one long-run player, all purifiable equilibria are Markov.

Evidence from both psychology and economics indicates that individuals give statements that appear to overestimate their ability compared to that of others. We test three theories that predict such relative overconfidence. The first theory argues that overconfidence can be generated by Bayesian updating from a common prior and truthful statements if individuals do not know their true type. The second theory suggests that self-image concerns asymmetrically affect the choice to receive new information about one's abilities, and this asymmetry can produce overconfidence. The third theory is that overconfidence is induced by the desire to send positive signals to others about one's own skill; this suggests either a bias in judgement, strategic lying, or both. We formulate this theory precisely. Using a large data set of relative ability judgements about two cognitive tests, we reject the restrictions imposed by the Bayesian model and also reject a key prediction of the self-image models that individuals with optimistic beliefs will be less likely to search for further information about their skill because this information might shatter their self-image. We provide evidence that personality traits strongly affect relative ability judgements in a pattern that is consistent with the third theory of social signalling. Our results together suggest that overconfidence in statements is more likely to be induced by social concerns than by either of the other two factors.