城市化与畜产品生产预测:健康与环境风险调整法

集约化农业生产所带来的环境影响和健康危害已经使人们逐渐认识到建立可持续农业发展途径的必要性.随着人们收入的增长,城市化的迅速发展成为消费模式转变的最为显见的驱动力.揭示在考虑到可持续发展的风险和不确定性的情况下对未来农业生产规划的预测,和在决策过程中恰当的风险指标,而这些内容的引入将极可能改变与畜产品设备配置和集约化程度相关的未来政策.以中国为例,研究主要目标为:(1)阐明如何将风险指标引入到决策过程中从而避免健康风险带来的负面结果;(2)阐明如何在农业生产规划中明确风险和不确定性,以达到可持续农业发展.     

The influence of immigration and international tourism on the demand for imported food products

The role of immigration and international tourism in food product imports, as two factors which potentially influence the (trans-) formation of tastes in a country, is theoretically and empirically analysed. In using an econometric error-correction specification of an import demand function, the scale of the impact of these two factors is estimated for the case of Germany (annual data from 1967 to 1990). The results show that, while aggregate food import demand from India, Thailand, China and Turkey is inelastic with regard to migration to Germany and international travel activities of Germans to these destinations, the estimated average elasticities for imports of wine, cheese and processed/preserved vegetables from France and Italy are all well above unity, thus suggesting that immigration and international tourism may indeed affect the import demand for certain food products.     

Regional taxonomy : A comparison of some hierarchic and non-hierarchic strategies

The effects of subjective decisions, particularly in the case of regional taxonomic methodology are often underestimated. Therefore the aptitude of alternative methods needs more careful evaluation. Comparisons of competing methods would provide important guidelines. A general evaluative approach based upon the discrepancy between the original resemblance and the derived cophenetic matrix is outlined for the hierarchic regional taxonomic case. Five main aggregative linkage strategies are appraised by means of quantitative measures. Furthermore two iterative non-hierarchic methods are compared for handling non-hierarchic regional taxonomic problems, where particular attention is paid to the influence of different initial partitions upon the (sub) optimal result.     

Technology transactions: networks over markets

There is a widespread belief in the business community that firms can rely on the market for buying and selling technological opportunities. The argument is: with so much technology development going on in the world, ‘there must be somebody somewhere who has the technology we need.’ According to this belief, acquiring new technology just boils down to finding the supplier, possibly with the help of a specialized intermediary. Several large firms have indeed developed ambitious mechanisms for acquiring the needed technological know-how as they proceed to make and market a new product. We contend that this concept of the technology transfer process is erroneous, as it conflicts with actual practice. The very high transaction costs entailed leave considerable room for opportunistic behavior and are more likely to occur when the parties do not know each other. An effective way to reduce transaction costs, therefore, is to limit technology transfers to the firm's partners, i.e. organizations with which the firm has already interacted in the past. Our research provides evidence that successful technology transfers typically take place between suppliers and buyers who had business relationships before considering a technology agreement. In addition, we report findings that companies using intermediaries (technological opportunities catalogues, databases, fairs, etc.) have been disappointed in their attempts to find new technologies from unknown sources. Because of the high risk of opportunistic behavior, it is practically impossible to assess the value of a technology without knowing who sells it. Similarly, the technology transfer capabilities of a company are difficult to appraise without prior knowledge through business interaction. To a certain extent, it may be better to buy any technology from a partner that one knows well than to buy a supposedly good technology from a firm with which one has had no experience. To put it bluntly: the identity of the partner may actually matter more than the technology being traded! Consequently, the relevant framework for technology transfer is built on a ‘network concept’ rather than the ‘market concept’. Firms wishing to acquire new technology should turn first to their network of trusted business partners, looking for available technological opportunities instead of trying to buy technology from unrelated organizations.     

Towards an understanding of the real effects and costs of inflation

Zusammenfassung Zum Verst?ndnis der realen Wirkungen und Kosten der Inflation. — Die traditionelle Ansicht, da\ eine Inflation, weil Geld neutral ist, keine nennenswerten realen Wirkungen hervorbringt, erweist sich nur für eine Volkswirtschaft als ann?hernd richtig, deren Regelungen vollst?ndig inflationssicher sind, d. h. für eine vollindexierte Wirtschaft. Die Realwirkungen erweisen sich aber als um so verbreiteter und schwererwiegend, je mehr bei wirtschaftlichen Regelungen Nominalwerte verwendet werden. Der Aufsatz untersucht nacheinander die Folgen von amtlichen Regelungen auf Nominalbasis (Steuersystem, Definition des steuerpflichtigen Einkommens, Buchführungsmethoden), von privaten Einrichtungen und übereinkünften auf Nominalbasis (Hypotheken, Rentenvertr?ge, Einkommensberechnungen), selbst für den Fall, da\ die Inflation vollst?ndig antizipiert wird bzw. wurde. Anschlie\end werden die Wirkungen einer nicht antizipierten Inflation geprüft, die in den bestehenden nominalen langfristigen Vertr?gen nicht berücksichtigt worden ist, und die Wirkungen einer Ungewissen zukünftigen Inflation. Soweit es m?glich ist, wird versucht, die sozialen Kosten von verschiedenen Realwirkungen abzusch?tzen, obwohl es zur Zeit nicht m?glich ist, die allgemeinen sozialen Kosten der Inflation zu ermitteln.

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Résumé Vers une compréhension des effets réels et des co?t d’inflation. — Nous démontrons que la vue traditionelle d’après laquelle l’inflation ne produit pas des effets réels appréciables à cause de la neutralité d’argent est valide pour une économie seulement dont les institutions sont complètement étanche à l’inflation, c’est-à-dire il s’agit d’une économie indexée. Mais nous démontrons que les effets réels deviennent plus et plus diffusés et sérieux comme les institutions de l’économie deviennent presque plus nominales. L’article examine succédamment les conséquences des institutions nominales de gouvernement (le système fiscal, la définition de revenu taxable, la procédure comptable); des institutions privées nominales et des conventions comptables (les contrats de hypothèque et d’annuité, le mesurage de revenu), même si l’inflation est, et a été complètement anticipée. En plus l’article examine les effets de l’inflation pas anticipée et pas incorporée dans les contrats nominaux existants à long terme, et de l’inflation future incertaine. S’il est possible, nous entreprenons l’effort de fixer les co?t sociaux des effets réels différents même bien qu’il ne soit pas possible au moment présent de fixer tous les co?t sociaux de l’inflation.

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Resumen Hacia el entendimiento de los verdaderos efectos y costos de la inflatión. — La visión tradicional que la inflatión no produce efectos reales apreciables debido a que el dinero es neutral, es solamente válida en forma aproximada para una economía cuyas instituciones están completamente a prueba de inflatión, p.ej. una economía completamente indexada. Pero se muestra que los verdaderos efectos se generalizarán más y más y serán más serios en la medida que las instituciones de la economía sean más cercanamente nominales. El artículo examina en forma sucesiva las consecuencias de instituciones gubernamentales nominales (sistema de impuestos, definitión del ingreso imponible, procedimientos contables); de instituciones privadas nominales y convenciones contables (hipotecas y contratos de renta anuales, medición del ingreso), incluso cuando la inflatión es y ha sido totalmente anticipada. Examina en seguida los efectos de inflatión no anticipados, que no han sido incoirporados dentro de los contratos de largo plazo existentes, y de inflatión futura incierta. En los casos que fue posible, se hizo un esfuerzo por determinar el costo social de varios efectos reales, aunque en este momento no es posible apreciar los costos sociales totales de la inflatión.

     

The effects of dividend yield and dividend policy on common stock prices and returns

This paper suggests that it is not possible to demonstrate, using the best available empirical methods, that the expected returns on high yield common stocks differ from the expected returns on low yield common stocks either before or after taxes. A taxable investor who concentrates his portfolio in low yield securities cannot tell from the data whether he is increasing or decreasing his expected after-tax return by so doing. A tax exempt investor who concentrates his portfolio in high yield securities cannot tell from the data whether he is increasing or decreasing his expected return. We argue that the best method for testing the effects of dividend policy on stock prices is to test the effects of dividend yield on stock returns. Thus the fact that we cannot tell, using the best available methods, what effects dividend yield has on stock returns implies that we cannot tell what effect, if any, a change in dividend policy will have on a corporation's stock price.     

Recent developments in monetary theory

This paper surveys recent work in monetary theory, with primary emphasis on material that has appeared since the writing of Harry Johnson's 1962 survey. The discussion deals with the following topics: (1) the theory of money demand, with special attention to inventory approaches; (2) money, inflation and growth; (3) the welfare cost of inflation, the optimum quantity of money, and inflationary finance; (4) disequilibrium theory; (5) the general equilibrium approach to monetary theory; (6) the new microfoundations of money; and (7) rational expectations and the Phillips Curve.     

An extended likelihood framework for modelling discretely observed credit rating transitions

The estimation of the parameters of a continuous-time Markov chain from discrete-time observations, also known as the embedding problem for Markov chains, plays in particular an important role for the modeling of credit rating transitions. This missing data problem boils down to a latent variable setting and thus, maximum likelihood estimation is usually conducted using the expectation-maximization (EM) algorithm. We illustrate that the EM algorithm is likely to get stuck in local maxima of the likelihood function in this specific problem setting and adapt a stochastic approximation simulated annealing scheme (SASEM) as well as a genetic algorithm (GA) to combat this issue. Above that, our main contribution is to extend our method GA by a rejection sampling scheme, which allows one to derive stochastic monotone maximum likelihood estimates in order to obtain proper (non-crossing) multi-year probabilities of default. We advocate the use of this procedure as direct constrained optimization (of the likelihood function) will not be numerically stable due to the large number of side conditions. Furthermore, the monotonicity constraint enables one to combine structural knowledge of the ordinality of credit ratings with real-life data into a statistical estimator, which has a stabilizing effect on far off-diagonal generator matrix elements. We illustrate our methods by Standard and Poor’s credit rating data as well as a simulation study and benchmark our novel procedure against an already existing smoothing algorithm.