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.  These  surveys  summarize  not  only received results  but  also newer developments, from recent journal articles and discussion papers. Some original
material is also included, but the main goal is to provide comprehensive and accessible surveys. The Handbooks are intended to provide not only useful reference volumes for professional collections but also possible supplementary readings for advanced courses for graduate students in economics.