When writing the preface the main work has been done. What remains is thanking all those people who directly or indirectly contributed to the out­ come. My thanks go to my family and friends for their encouragement towards the completion of this book. Among the academic profession, I would like to thank Prof. Dr. Dr. Harald Scherf, my academic teacher, first. During the years at Hamburg University I benefitted especially from his profound knowledge of Keynesian theory. His way of examining an argument in an unbiased way helped me a lot to carry out the reseach I wanted to do. His confidence enabled me to finish the work. A part of the book was written while I was a visiting fellow at DELTA, Paris, where I am particularly indebted to Roger Guesnerie. I have benefitted from his encouragement, advice, and gentle criticism during discussions and seminars, especially on the topic of the time structure of economic dynamics. I would like to acknowledge the hospitality and stimulating atmosphere at DELTA. Different versions of the manuscript, or parts of it have been read by Prof. Dr. Manfred Holler, Dr. Jorg Bibow and Dr. Gabriele Kasten. Their comments and suggestions were quite helpul and are gratefully acknowledged. Additionally, I have to thank Prof. Dr. M. Funke and Prof. Dr. V. Timmer­ mann.