Dr. Kooyman has made a careful study of the econometric model used
around 1963 by the Netherlands Central Planning Bureau, especially of
eight of its most import- ant behavioural equations. The Bureau used
coefficients estimated from a pre-war and a post-war time series
simultaneously, in order to have a larger number of observations. The
author, being aware of the difference in general economic 'climate' in
the two periods, tests the assumption of no difference in pre-war and
post-war coefficients. In an inventive way he uses a few alternat- ive
approaches. On the basis of his findings he concludes that a new
specification of some of the equations is necessary. Since the Dutch
model is likely to be the oldest of its type, foreign readers may be
interested in reading Dr. Kooyman's text - slightly adapted - in
English. J. Tinbergen v Preface The first edition of this book appeared
in Dutch as a thesis which was defended at the State University of
Groningen in 1971. When working on this publication I received much help
from Dr. H. Rijken van Olst and Dr. G. F. W. M. Pikkemaat, professors at
the State University of Groningen of, respectively, statistics and
econometrics, and mathematical economics. I would like to thank Prof.
dr. J. Tinbergen, who aroused my enthusiasm for quantitative economics
during my college years at the Netherlands School of Economics: I am
much obliged to him for his willingness to write a foreword.