Many interactive environments can be represented as games, but they are so large and complex that individual players are in the dark about others' actions and the payoff structure.  This paper analyzes learning behavior in such 'black box' environments, where players' only source of information...

Consider a finite, normal form game G in which each player position is occupied by a population of N individuals, and the payoff to any given individual is the expected payoff from playing against a group drawn at random from the other positions.  Assume that individuals adjust their behavior...

Alpha is the amount by which the returns from a given asset exceed the returns from the wider market.  The standard way of estimating alpha is to correct for correlation with the market by regressing the asset's returns against the market returns over an extended period of time and then apply...

Stochastic learning models provide sharp predictions about equilibrium selection when the noise level of the learning process is taken to zero.  The difficulty is that, when the noise is extremely small, it can take an extremely long time for a large population to reach the stochastically...

Traditional methods for analyzing portfolio returns often rely on multifactor risk assessment, and tests of significance are typically based on variants of the t-test.  This approach has serious limitations when analyzing the returns from dynamically traded portfolios that include derivative...

Interconnections among financial institutions create potential channels for contagion and amplification of shocks to the financial system.  We propose precise definitions of these concepts and analyze their magnitude.  Contagion occurs when a shock to the assets of a single firm causes other...

The diffusion of an innovation can be represented by a process in which agents choose perturbed best responses to what their neighbors are currently doing.  Diffusion is said to be fast if the expected waiting time until the innovation spreads widely is bounded above independently of the size...

Social norms are patterns of behavior that are self-enforcing at the group level: everyone wants to conform when they expect everyone else to conform.  There are multiple mechanisms that sustain social norms, including a desire to coordinate, fear of being sanctioned, signaling membership in...

In recent years bonuses tied to performance have become commonplace in banks and other financial institutions; indeed they now constitute a major part of employee compensation.  The practice was originally justified by academic work on principal-agent contracts, which argued that performance...

We propose a simple payoff-based learning rule that is completely decentralized, and that leads to an efficient configuaration of actions in any n-person finite strategic-form game with generic payoffs.  The algorithm follows the theme of exploration versus exploitation and is hence stochastic...