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This article appeared originally in 1930, in Dutch, under the title “Mathematiese Psychologie” in Mens en Maatschappij. Translated and annotated by Conrad Heilmann, Stefan Wintein, Ruth Hinz, and Erwin Dekker, it is accompanied—in the present issue—by the article “No Envy: Jan Tinbergen on Fairness” written by Conrad Heilmann and Stefan Wintein.

While I consider very useful any attempt to answer the question of what the future development of the science of economics will be, I expect rather divergent answers from those invited to formulate an answer. Almost as a matter of course every worker in some fields of our discipline will consider his speciality the most important — for this is the reason why he works on it. His choice will partly be based on what problems the present world is faced with and so illustrates Gunnar Myrdal’s old statement on the forces at work in such choices.1 But there remain subjective preferences of a more random nature which co-determine our personal curiosity and there remain the environments from which each of us has originated; environments which differ. And there are elements of the technique of scientific work which fit one student better than another. Thus, for example, I am not going to touch monetary problems, since I feel less fit to deal with them; this does not imply that, in my opinion, monetary problems are not important: on the contrary. Yet, I am going to take up some problems emotionally closer to my personal approach.

Jan Tinbergen, laureat du prix Nobel d'economie en 1969, a participe, a la fin de cette annee-la, a une reunion organisee pour conseiller le BIT sur les priorites que devait se fixer, en matiere de recherche, le Programme mondial de l'emploi qui venait d'etre cree. Dans sa communication, il traita des rapports entre la politique commerciale internationale et la creation d'emplois [… lire la suite].

Jan Tinbergen, galardonado con el primer Premio Nobel de Economia en 1969, participo a finales de ese mismo ano en una reunion de economistas que la OIT habia convocado con el fin de fijar las prioridades en materia de investigacion del recien creado Programa Mundial del Empleo. En su ponencia Tinbergen examino la influencia de la politica comercial internacional en la capacidad de creacion de empleo. En su opinion, […] Seguir leyendo

At the end of 1969, Jan Tinbergen, who received the Nobel Prize for economics that same year, participated in a meeting to advise the ILO on research priorities for its newly created World Employment Programme. His presentation dealt with international trade policy and its effects on job creation. [more]

Publisher Summary This chapter discusses project appraisal. One phase in the construction of a development plan consists of the selection of a program of projects out of a larger collection of projects. The aim of this selection process is to find a set of projects that together will use the quantities available of scarce production factors and that will maximize the contribution to the aims of development policy. The prices, often indicated as “shadow prices,” must reflect the relative scarcities of the factors and they depend on the selection of the projects made. The modern trend is to develop less general, numerical methods of a trial-and-error method, and to aim at the exact answer. In the tradition of successive approximations, the chapter discusses the problem in its simplest form. In an attempt to generalize the results to more complicated frequency distributions, it is an established tradition to develop the frequency density function into a power series.

Many ecologists mark their free living study animals with the aim to collect knowledge on individual life histories. Yet, marking animals may affect life histories and it is important to quantify such effects. Literature on this subject is relatively rare, especially when it concerns the effect of bird rings. This is partly because control groups are often missing, since the rings were not applied with the goal to measure their effect on life histories. From studies in captivity there is evidence that the colour of rings may affect partner choice and in the field certain outstanding colours of rings may affect predation risk. Here we use data of an ongoing study of Great Tits Parus major to analyse whether the colour of rings fitted in different combinations to nestling Great Tits (day 14, n = 9818) affected their life histories in terms of natal dispersal, first year local recapture rate, breeding performance and second year local recapture rate. We measured reflectance spectra to quantify the brightness of the colour rings, and we used a human panel to judge the conspicuousness of the rings against a grey background. We found support for a positive effect of the conspicuousness, as judged by human observers, of the colour ring combination on local recapture rate, but not on natal dispersal suggesting that survival was affected. No effect was detected on breeding performance. The brightness of the rings did not explain variation in life history components. Although the effect of conspicuousness was statistically weak, the effect size is of potential biological importance. Life expectancy of individuals without conspicuous rings is estimated to be 28% shorter than for individuals with three conspicuous rings. Our result could have a considerable impact on life history studies where fitness measures are based on colour-marked bird populations. Colour of the colour rings will affect the variance of fitness estimates and may even bias the mean of fitness estimates when specific colours are used in specific periods, in specific environments or to mark particular categories of birds like year classes.

Reprint of the orginally published version in International Social Science Journal (UNESCO), Vol. 11, No.3, 1959, pp. 351-360. In French: La Planification de la Politique Economique, Revue Internationale des Sciences Sociales, 1998, pp. 383-392

SummaryThe feathers of Amazon parrots are brightly coloured. They contain a unique class of pigments, the psittacofulvins, deposited in both barbs and barbules, causing yellow or red coloured feathers. In specific feather areas spongy nanostructured barb cells exist, reflecting either in the blue or blue-green wavelength range. The blue-green spongy structures are partly enveloped by a blue-absorbing, yellow-colouring pigment acting as a spectral filter, thus yielding a green coloured barb. Applying reflection and transmission spectroscopy, we characterized the Amazons' pigments and spongy structures, and investigated how they contribute to the feather coloration. The reflectance spectra of Amazon feathers are presumably tuned to the sensitivity spectra of the visual photoreceptors.

The author considers the problem of the duration of development and its consequences for development assistance, in the developing as well as developed countries. Emphasis is given to the influence of development aid and it is argued that the time dimension has important policy implications and requires further thoroughgoing theoretical analysis.

SUMMARYThe colours of the common kingfisher, Alcedo atthis, reside in the barbs of the three main types of feather: the orange breast feathers, the cyan back feathers and the blue tail feathers. Scanning electron microscopy showed that the orange barbs contain small pigment granules. The cyan and blue barbs contain spongy nanostructures with slightly different dimensions, causing different reflectance spectra. Imaging scatterometry showed that the pigmented barbs create a diffuse orange scattering and the spongy barb structures create iridescence. The extent of the angle-dependent light scattering increases with decreasing wavelength. All barbs have a cortical envelope with a thickness of a few micrometres. The reflectance spectra of the cortex of the barbs show oscillations when measured from small areas, but when measured from larger areas the spectra become wavelength independent. This can be directly understood with thin film modelling, assuming a somewhat variable cortex thickness. The cortex reflectance appears to be small but not negligible with respect to the pigmentary and structural barb reflectance.

Contents: Acknowledgements General Introduction Howard R. Vane and Chris Mulhearn PART I RAGNAR A.K. FRISCH Introduction to Part I: Ragnar A.K. Frisch (1895 - 1973) 1. Ragnar Frisch (1933), 'Propagation Problems and Impulse Problems in Dynamic Economics' 2. Ragnar Frisch (1934), 'Circulation Planning: Proposal for a National Organization of a Commodity and Service Exchange' and 'Circulation Planning: Part III. Mathematical Appendix' 3. Ragnar Frisch (1936a), 'Annual Survey of General Economic Theory: The Problem of Index Numbers' 4. Ragnar Frisch (1936b), 'On the Notion of Equilibrium and Disequilibrium' 5. Ragnar Frisch (1981), 'From Utopian Theory to Practical Applications: The Case of Econometrics' PART II JAN TINBERGEN Introduction to Part II: Jan Tinbergen (1903-94) 6. J. Tinbergen (1940a), 'Econometric Business Cycle Research' 7. J. Tinbergen (1940b), 'On a Method of Statistical Business-Cycle Research: A Reply' 8. Jan Tinbergen (1952), 'The Logical Structure of the Normal Quantitative Policy Problem (Targets and Instruments in Equal Numbers) Directives' and 'Inequality Between Number of Targets and Number of Instruments: Alternative Instruments or Incompatible Targets' 9. Jan Tinbergen (1959), 'An Economic Policy for 1936' PART III LAWRENCE R. KLEIN Introduction to Part III: Lawrence R. Klein (b. 1920) 10. Lawrence R. Klein (1947), 'Theories of Effective Demand and Employment' 11. Harold Barger and Lawrence R. Klein (1954), 'A Quarterly Model for the United States Economy' 12. L.R. Klein (1958), 'The Estimation of Distributed Lags' 13. Lawrence R. Klein (1964), 'A Postwar Quarterly Model: Description and Applications' 14. Gary Fromm and Lawrence R. Klein (1965), 'The Brookings-S.S.R.C. Quarterly Econometric Model of the United States: Model Properties' 15. Phoebus J. Dhrymes, Lawrence R. Klein and Kenneth Steiglitz (1970), 'Estimation of Distributed Lags'

Dankzij zijn uitzonderlijke intellectuele talent en zijn uitermate heldere denk- en schrijfstijl, gecombineerd met een grote discipline en bescheidenheid, heeft Jan Tinbergen wereldwijd invloed uitgeoefend op het denken over economische politiek. Zijn levensmotto luidde: 'De economische wetenschap in dienst stellen van een leefbare aarde.' Dit boek is een bijzonder en hartstochtelijk pleidooi voor een wereldwijde aanpak van de strijd tegen armoede.

textabstractIn the last five years humanity has become faced with the problem of the optimal socioeconomic order more clearly than ever. After the confrontation of capitalism and socialism, which was the core of the Marxist thesis, the fact transpired that capitalism was not the optimal order. It was eliminated in two different ways. In Western economies capitalism was reformed stepwise by pulling its sharpest teeth, while maintaining the stimulating forces in the markets. As to communist economies - the Soviet Union changed capitalism via the 1917 October revolution and China followed. In 1986, Mikhail Gorbachev's view that the communist system did not work was accepted by the Soviet Union communist party congress. Now, in 1992, the world is discussing, more urgently than ever, what the best ('optimal') socio-economic order is; how much reintroduction of capitalism is necessary to attain the best order? This essay discusses the simplest possible model that can contribute to the discussion. The advantage of building the simplest possible model is twofold. Firstly, such a model can state the nature or essence of an optimal order. Secondly, it can indicate the order of magnitude of the main characteristic of an optimal order. The main characteristic - the question that separated socialists from other politicians - is the redistribution of income. Within a single nation, redistribution is achieved by taxes and social security contributions. In the world economy, redistribution is accomplished by development assistance and trade policy. In this essay the language used is that of the industrial economy, in which the two groups considered are labour and capital. The model can be translated into another in which the two groups are the developed and underdeveloped countries. It may even be translated into a security model of two powers, in which redistribution is obtained by security assistance (see J. Tinbergen, World Security and Equity, Aldershot, 1990), or a colonial system. In the last version not the common welfare will be maximized, but the welfare of the colonial powers, which leads to negative redistribution (the exploitation of the colonies).

Throughout history small territories were integrated into larger units. Sometimes disintegration occurred. A quantitative characteristic of this process is its velocity,i.e. the reductionr of independent territories per annum or the growthg of the number of members of a larger unit. These figures were measured for France, Switzerland, Europe 1500-1900 and for the Western European integration. Velocities vary between 1.0002 and 1.0676. Variations can be partly explained, but require further explanation. Velocities may be used to estimate the time needed for the acceptance of additional members, the completion of European integration and world integration.

textabstractTinbergen (1988) describes his method of conducting economic research. In contrast to Dopfer (1988), the subject of mechanics is avoided, and the method deals only with economics. The purpose of economic research is seen as either: 1. an attempt to explain an economic phenomenon, or 2. the recommendation of an economic policy or structure. No use is made of any philosophy of science concepts. An important characteristic of Tinbergen's views is that he deals with qualitative and quantitative aspects of economic research. The difference between quantitative and qualitative problems is that the former are solved completely only after measurement and mathematical solution with the aid of a model, whereas the latter do not require the tools of measurement and mathematical solution. In a reply, Dopfer comments on Tinbergen's belief that both quantitative and qualitative research is important in economics. He notes that such an insight can have various interpretations, depending on the viewpoint of the researcher.

The necessity of new thinking exists in military matters, but also in what must replace military activity: institutions and policies. Their base must be confidence inspiring, their aim a world without war, with a clean environment, an equitable distribution of welfare over today's world population and over today's and all future generations. Within the framework of these restrictions welfare must be maximised. The means to attain the aim are the institutions which together may be called the Earth's management. This may be the outcome of a completed integration or it may be deliberately organised, preferably by reforms and a strengthening of the United Nations. A World Treasury and a World Police Force should be added to the present set of institutions. Authorities vested with the power to implement supranational decisions are necessary if many countries’ welfare is affected. More development assistance should be financed from savings on arms.

When cleaning up my archives I came across a short article of April 1991 co-authored with Jan Tinbergen, on what the Soviet Union might learn from OECD countries in economics and politics. The article apparently never got published, partly since the Soviet Union collapsed in December 1991. Jan Tinbergen died in 1994. Reading the article again in 2005 shows that some arguments still have value. In 2005, an advice, purely my own now, would be that Russia and the other republics of the former Soviet Union apply for membership of the European Union.

L'A. montre qu'en 1970, l'O.N.U. a fixe a 0.7% du produit national brut le montant de l'aide annuel au developpement (Official Development Assistance) que les pays membres de l'O.C.D.E. octroient aux pays en voie de developpement. Il estime que ce montant devrait etre porte a 1.27% du produit national brut des pays les plus riches pour favoriser le developpement des nations les plus pauvres. Il presente un certain nombre de donnees collectees entre 1987 et 1990 concernant l'aide aux pays en voie de developpement

The author considers the problem of the duration of development and its consequences for development assistance, in the developing as well as developed countries. Emphasis is given to the influence of development aid and it is argued that the time dimension has important policy implications and requires further thoroughgoing theoretical analysis.

The changes in temperature occurring in the body of a flying blowfly are measured with the non-invasive technique of thermal imaging. It is found that during rest the temperatures of the three main body compartments, i.e. head, thorax and abdomen, approximately equal the ambient temperature. Upon flight onset the thorax temperature increases about exponentially, with a time constant ≈ 30 s. In steady flight, the thorax temperature is ≈ 5 °C higher than the ambient temperature (≈ 25 °C). After flight, the temperature of the thorax decreases, again about exponentially, with a time constant of ≈ 50 s. A three compartment model of the insect body allows a quantitative description of these temperature changes, thus yielding values for the blowfly’s thermal parameters.

In the well-known publication ‘World Product and Income’, Kravis, Heston and Summers (1982) showed figures for the real incomes per capita for various groups of countries (p. 343); since that time they have updated and extended these estimates. The most recent ones are presented in UNDP’s Human Development Report 1992 (pp. 178 and 197). The relevant figures for this essay are repeated in Table 8.1, together with some figures derived from them.

Until recently the world population faced four great problems. These will be indicated as the Security, the Poverty, the Environment and the Sustainability problems.

A considerable part of recent research as well as of teaching in the field of quantitative economics in the Netherlands has been grouped around the objective of supplying tools for economic policy. This applies to short-term as well as to long-term economic policy and to policies for developed as well as for under-developed economies. The elements needed for such research cover most of the subjects traditionally included in teaching programmes of this kind, but give them a certain twist and direction. It is the intention of this article to give a brief survey of teaching and research activities as they now exist in this country, more particularly at the Netherlands School of Economics, while indicating the links with practical activities in the field of economic policy.

After the discovery by the communist leader, Mikhail Gorbachev, that the productivity of a centrally-planned economy is considerably less than that of free market economies, the impression given is that all markets should be free. This, however, is a misunderstanding which is harmful to all economies. The misunderstanding is that there are two types of markets, stable and unstable, and that only the stable markets should be free. The category of unstable markets is not unimportant, and so it is vital to make a distinction between the two.

1. Simultaneous measurements of the receptor potential and the light-induced mitochondrial activation were performed in white-eyed blowflies Calliphora vicina, mutant chalky, and Lucilia cuprina, mutants wFand w'nss. The intensity dependence and the temporal dynamics were investigated. 2. The characteristic curve of the light-induced mitochondrial activation vs. log intensity has an S-like shape, which is much steeper than the characteristic curve of the receptor potential (the V/log I curve). The threshold intensity of mitochondrial activation elicits about a half-maximal receptor potential, while mitochondrial activation and photoreceptor potential saturate at about the same intensity. 3. The time course of the mitochondrial activation induced by a light flash, i.e. the pulse-response curve, is biphasic in both mutants with normal phototransduction properties, Calliphora chalky and Lucilia wF; the shape is slightly species dependent. 4. In the phototransduction mutant Lucilia w'nss the step-responses of both the (bright) light-induced mitochondrial activation and receptor potential are quite different from the corresponding signals in Lucilia wF. The striking resemblance of the step-response of the mitochondrial activation to its pulse-response indicates that mitochondrial activation and receptor potential are intimately linked.

It is customary to introduce into a relationship we are going to test with the aid of regression analysis, added to the systematic terms, an error term. The systematic terms are those containing one or more independent variables; in a relation used to explain national income as a dependent variable we may use as an important independent variable exports. This will especially apply to small open countries. The error term is introduced as a catchall for less important independent variables and for measuring errors of both the dependent variable and the independent variables. The error term is usually assumed to be a random variable with an average value of zero and a normal distribution.

In this article in honour of Nurul Islam I make an attempt to contribute to a subject that both of us — and many other economists — have worked on for many years: development co-operation. My contribution deals with a lacuna I try to fill up, at least partly. The lacuna is that we don’t know what is the optimal amount of development assistance. For years we have used, in many discussions, the criterion of 0.7 per cent of donor countries’ GNP. It was proposed for the (First) Development Decade by H.W. Singer and his collaborators, for the Second Development Decade (1971–1980) by the Pearson Commission and recommended by the Brandt Commission. But it was hardly based on some optimality criterion. It was closer to a satisficing than to a maximising criterion; satisficing, to be sure, the donor countries. Moreover, most of the donor countries did not live up to what their own experts had recommended.

This article examines the demand-supply theory of incomes tested by the 1970 U.S. census figures. Contrary to previous U.S. population censuses, the 1970 volumes include one in which, for a large of occupational groups, tables are published showing earnings by education classes and age groups for race and sex groups. Earnings for the modal occupational group were considered as income for each education category. The supply factor was taken equal to the numbers of persons in each educational category employed in 1969 in specification of the theory. The crucial assumption made was that the educational structure of employment within each main occupational group was the same as in 1969. In both specifications the demand factor was estimated by a projection, five years ahead, of employment in each of the educational groups, using the same method as just described for specification of the supply factor, but assuming a lead instead of a lag. The desired composition of the labour force as seen by employers was derived from plans for the future taking into account changes in occupations to be expected on the basis of the trend 1950-70, but assuming the same educational structure within each of the main occupational groups.