Introduction to the series The aim of the Handbooks in Economics series is to produce Handbooks for various branches of economics each of which is a definitive source reference and teaching supplement for use by professional researchers and advanced graduate students. Each Handbook provides self contained surveys of the current state of a branch of economics in the form of chapters prepared by leading specialists on various aspects of this branch of economics. The Handbooks provide not only useful reference volumes for professional collections but also possible supplementary readings for advanced courses for graduate students in economics.