... love for languages and arts was transmitted onto his children; his occasional outdoor drawing lessons and the walks and bike rides with his children during the summer holidays contributed to the pleasant and intellectual atmosphere which characterized the education. The mother, Jeanette van Eek, personified the order and regularity of the family in terms of both her modest way of conducting the Tinbergen household and her mathematical interest.

I wanted to finish quickly and then to switch to economics. Now you can ask why I chose physics at all, but it was clearly my real interest. I liked physics and mathematics very much and I also felt that that was the thing I was perhaps strongest at, but at the same time I had already come to the conviction that I could probably be more useful to society by being an economist. I think most of the bigger political discussions were economic rather than physical, and so I hoped to get sufficient capability to handle things with mathematics and perhaps take physics as an example of a more developed science than economics.

To Ehrenfest I owe a great deal. I studied physics at a time when a number of fascinating persons were there together. Ehrenfest would not instruct as such, as he preferred dialogue. Thanks to him I could participate in discussions with Albert Einstein. Also Kamerling Onnes, Lorentz and Zeeman were present. Being a student in the hands of such teachers, you are very fortunate indeed.

In 1923 I had become a member of the Labour Party and its youth organization; I had come into contact with the poor part of Leiden, not usually known so well by students. In retrospect I wonder whether I would have been clever enough to contribute to modern physics; anyway, my interest went to helping to change society.

I was responsible for the periodical 'De Nederlandsche Conjunctuur'. It started in 1929, but the War made an end to it. My official responsibility as editor left me quite some freedom. The man supervising my work was in charge of building up something like the London and Cambridge Economic Service, concerned with the cyclical prospects of the Dutch economy.

Life at the Central Bureau of Statistics at The Hague during the thirties was anything but dull. The problems of unemployment caused by the Great Depression had enforced the call for statistics for policy purposes. Although the Central Bureau of Statistics had been working on business cycle statistics for some time, it was only given its major impulse with the institution of a unit of business cycle research. Tinbergen, who had only just finished his dissertation and entered the staff of statisticians, was given charge of this new unit. Clearly influenced by the German business cycle research institutes in Berlin and Frankfurt, Tinbergen gradually tried to develop an empirical approach to dynamic problems in economics. At the same time he surrounded himself with young engineers, mathematicians and physicists, such as Johannes Bernardus Dirk Derksen, Pieter De Wolff and A Bijl. Together they formed the so called "Q.C." or "Quantitatieven Club", an informal group of young men both socially concerned as well as quantitatively or mathematically oriented. Together with others, such as Tjalling Koopmans, they engaged in small discussion groups evaluating the poverty of contemporary economics and the need for a more rigorous approach.

'Econometrica', the journal of the new society, provided a much needed forum for the presentation and discussion of the results of the young science. Here and in the frequent meetings of the Econometric Society, ... Tinbergen made a strong impact both by [his] own contributions and by [his] inspiring personal influence on new cadres of econometricians.

The assumption that these principles of economic rationality might really be made to work was substantiated by Tinbergen one year afterwards in an academic debate on the possibilities of active economic policy. In his contribution to the debate Tinbergen projected a 'quantitative stylising of the Dutch economy' to isolate the important factors and their effects by means of a set of definitions and equations. This "model" of the Dutch economy, as he called it (written with quotation marks at first), would allow one to throw some data into the "mathematical machinery" which would then predict the results.

In private conversations, Tinbergen told me how much he admired the work of Keynes in his 'General Theory' 1936 and that he was so inspired by it that he was trying to provide some empirical substance and use estimated models to implement appropriate policies. It is a pity that Tinbergen's work received such shabby critical treatment by Keynes (in 1939), but being the kind person that he was, he expressed no ill will towards Keynes.

In an attempt to evaluate what model building has contributed to the theory and practice of economic science I feel that at least we can say that models have had a 'didactic' value. Often in our text books we bring simplified, not to say over-simplified, pictures of reality which nonetheless contribute to making understood some essential features of that reality. ... What I called "didactic value" also stands for 'communication' value. The ability of a planning expert to communicate with politicians and with citizens constitutes an important element in any type of democratic or semi-democratic planning and such communication can be enhanced by relatively simple models. In order not to misrepresent reality, however, there will be a need for a succession of models, as used in planning in 'stages' or, as we now say, multi-level planning. I do think, however, that the utility of models goes beyond their didactic value. They are a real and essential element in the preparation of well-coordinated policies. But they cannot do this job all by themselves. Models constitute a 'framework' or a 'skeleton' and the flesh and blood will have to be added by a lot of common sense and knowledge of details.

[It] is simultaneously a study of some mathematical problems met in constructing models for policy analysis; a demonstration of the application of mathematical models and other systematic, but non-mathematical, methods to a variety of illustrative policy problems; and an exposition of what the policy-making process is and ought to be. On the first, it is excellent; on the second, helpful but puzzling; on the third, I suggest, mistaken.

Tinbergen, who enjoyed success in both politics and science early in his career, exploited an almost natural opportunity to integrate the two. His career was based on a choice rather than a dilemma, and his work exerted a major impact on both economics and on mathematics. As econometrics grew, it helped to promote a new paradigm for making mathematics useful, mathematical modelling.

... on no less than six occasions has he brought economics a large step forward. Thus, (i) he was a pioneer in modern economic dynamics; (ii) he helped to establish econometrics; (iii) he is the founder of empirical macroeconomics; (iv) he contributed decisively to create the modern techniques of economic forecasting and prediction; (v) he is the founder of the modern theory of economic policy; (vi) he has contributed significantly to modern development planning in backward countries.

I am inclined to indicate sympathy for the underdog or the suffering as one and tolerance as another of the basic elements of my ethical belief. Although a member of a church that strongly emphasized tolerance, I am not sure whether I am religious; but I am sure I am a product of Christianity, interpreted in my own way. My democratic socialist political choice, my European federalist ideal, and my Third World priorities all have that source of inspiration. Looked at from the negative side some of the big evils in this world seem to me to be nationalism and war.

... is my interest in languages: this I share with my wife and inherited from my parents. Intellectually the comparative part of linguistics is the most interesting part: to compare the diverging meanings the same word has in English and French, or in German or Dutch, for instance "grand"; to compare Italian and Spanish, or Swedish and Danish. ... Anti-hobbies? Yes, I don't like any form of sport and I dislike cars. I have to admit that sometimes I am grateful for a lift: not a consistent attitude!

In a neat, simple house, virtually indistinguishable from others on his block in the middle class neighbourhood of The Haviklaan, The Hague, lives one of the world's most distinguished economists, a co-winner of the first Nobel Prize in Economics in 1969, and a man who is known for his gentleness, his modesty, and his selfless dedication to the cause of human welfare. That man is Jan Tinbergen. ... Jan Tinbergen is an unassuming man, who does not trumpet his achievements to the world. He almost never criticizes colleagues. He could earn substantial personal income with his talents, but instead he has chosen to devote himself to the service of others. He does not drive a car, but takes a bus or tram to work. He has been known to thank his undergraduate students for selecting his courses. He has studied many languages, mainly in order to communicate better with those he has worked with in many parts of the world. ... He is fond of drawing. He believes in human dignity. And he lives by that belief.