This is the set of three volumes containing edited versions of papers and commentaries presented in invited symposium sessions of the Eighth World Congress of the Econometric Society. The papers summarize and interpret recent key developments and discuss future directions in a wide range of topics in economics and econometrics. The papers cover both theory and applications. Written by leading specialists in their fields these volumes provide a unique survey of progress in the discipline. Mathias Dewatripont is Professor of Economics at the Universite Libre de Bruxelles where he was the founding Director of the European Centre for Advanced Research in Economics (ECARE). Lars Peter Hansen is Homer J. Livingston Distinguished Service Professor of Economics at the University of Chicago. Stephen J. Turnovsky is Castor Professor of Economics at the Univeristy of Washington and recently serves as an Editor of the Journal of Economic Dynamics and Control. Professors Dewatripont, Hansen, and Turnovsky are Fellows of the Econometric Society and were Program Co-Chairs of the Eighth World Congress of the Econometric Society, held in Seattle, Washington, in August, 2000.