This book contains the Proceedings of a symposium that was held in Rotterdam from 12 to 15 January 1982 to celebrate the 25-th anniversary of the Econometric Institute of the Erasmus University. The subject of the symposium, developments in econometrics and related fields, was particularly appropriate for the occasion. In 25 years the research carried out at the Econometric Institute developed from the original seminal work in econometrics, carried out under the supervision of the first director H. Theil, to embrace related areas such as mathematical economics, operations research, systems...