This book presents recent thought on market efficiency, using a complex systems approach to move past equilibrium models and quantify the actual efficiency of markets. The older view that markets are perfectly efficient has come under attack from several different directions, including studies of market anomalies, human psychology, bounded rationality, agent-based modeling, and evolutionary game theory. This volume brings together some of the best economists, physicists, and biologists working on quantitative models of complex, self-organized behavior relevant to measuring marketing efficiency, to stimulate new approaches to understanding financial markets.