PREFACE TO THE COLLECTION PREAMBLE The editors are pleased to present a selection of Henri Theil's contributions to economics and econometrics in three volumes. In Volume I we have provided an overview of Theil's contributions, a brief biography, an annotated bibliography of his research, and a selection of published and unpublished articles and chapters in books dealing with topics in econometrics. Volume II contains Theil's contributions to demand analysis and information theory. Volume III includes Theil's contributions in economic policy and forecasting, and management science. The selection of articles is intended to provide examples of Theil's many seminal and pathbreaking contributions to economics in such areas as econometrics, statistics, demand analysis, information theory, economic policy analysis, aggregation theory, forecasting, index numbers, management science, sociology, operations research, higher education and much more. The collection is also intended to serve as a tribute to him on the occasion of his 68th birthday: These three volumes also highlight some of Theil's contributions and service to the profession as a leader, advisor, administrator, teacher, and researcher. Theil's contributions, which encompass many disciplines, have been extensively cited both in scientific and professional journals. These citations often place Theil among 10 researchers (ranked according to number of times cited) in the world in various the top disciplines.

This study of demand analysis links economic theory to empirical analysis. It demonstrates how theory can be used to specify equation systems suitable for empirical analysis, and discusses demand systems estimation using both per capita time series and household budget data.

Studies in Global Econometrics is a collection of essays on the use of cross-country data based on purchasing power parities. The two major applications are the development over time of per capital gross domestic products, (including that of their inequalities among countries and regions) and the fitting of cross-country demand equations for broad groups of consumer goods. The introductory chapter provides highlights of the author's work as relating to these developments. One of the main topics of the work is a system of demand equations for broad groups of consumer goods fitted by means of cross-country data. These data are from the International Comparison Program, which provides PPP-based figures for a number of years and countries. Similar data are used for the measurement of the dispersion of national per capita incomes between and within seven geographic regions.