Sulla dipendenza continua della probabilità di rovina dal caricamento dei premi

Si studia un modo di approssimare la probabilità di rovina relativa a un caricamento ₀ con le probabilità di rovina relative a una successione di caricamenti ( _k ) _k , che approssimano ₀ quandok tende all'infinito.

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Summary In this paper we study a way of approximating the probability of ruin related to a loading ₀, by the probabilities of ruin related of a sequence of loadings ( _k ) _k which «approximate» ₀ ask converges to infinity.

     

Una luce nuova su una vecchia storia: La “scindibilitá” di Cantelli-insolera e la struttura a termine dei tassi d'interesse

Si mostra come la moderna teoria della struttura a termine dei tassi d'interesse consenta di definire diversi esempi (più o meno naturali) di leggi di capitalizzazione a tre variabili, e dunque sostanzialmente del tipo di quelle considerate da Insolera. La relativa condizione di scindibilità, già oggetto di polemica con Cantelli, appare formulabile in più di una versione, una delle quali equivale alla odierna ipotesi di equilibrio del mercato finanziario.

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Summary The modern theory of term structure of interest rates leads one, in a natural way, to consider several models of accumulation factors which depend on three variables, and can therefore be counted among those considered in this time by the Italian finance mathematician F. Insolera. The question of how to formulate the principle of consistency for such factors has been the subject of an animated debate between Insolera and F.P. Cantelli. The present paper shows that it admits more than one solution; one of the possible versions rendering the principle equivalent to the market equilibrium condition.

     

Some remarks on stochastic dominance

The present work proposes a definition of dominance (dominance in the strict sense), which is weaker than first order stochastic dominance, stating precisely that the r.v.Y dominatesX (XY) if Pr(YX)=1.Such a dominance in the strict sense is then compared with first and second order stochastic dominance and with dominance between descisions of the same decision problem summarised in a table of results, arriving at certain general remarks about decision problems and the choice between r.v.'s. Indications are also given about how it is possible to obtain simple and useful bounds for Pr(YX).

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Riassunto Nel presente lavoro si propone una definizione di dominanza (dominanza in senso stretto) più debole della dominanza stocastica del prim'ordine, precisamente dicendo che la v.a.Y dominaX (XY) se Pr(YX)=1.Si confronta poi tale dominanza in senso stretto con le dominanze stocastiche del primo e del secondo ordine e con la dominanza tra decisioni di uno stesso problema di decisione sintetizzato in una tabella dei risultati giungendo ad alcune precisazioni generali sui problemi di decisione e di scelta tra v.a. Si danno anche indicazioni su come sia possibile ottenere limitazioni per la Pr(YX).

     

Global dynamics in models of fluctuating growth Part II: Three dimensional systems

The dynamics of a model of fluctuating growth, where non-constant returns are allowed, is represented, under Goodwin's classical assumptions, by a non-autonomous two-dimensional system, which can be transformed into an autonomous three-dimensional one. We describe the global phase portrait of the latter, in the two cases of increasing and decreasing returns, proving, in particular, the absence of economically meaningful attractors. However the orbits exhibit different features in the two cases: namely they asymptotically converge to a singular point, where the economy dies, if the returns are decreasing, and diverge, spiralling around a certain line, if the returns are increasing.

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Riassunto Un modello non-lineare di crescita alla Goodwin, in cui i rendimenti possono essere non costanti, è rappresentato da un sistema dinamico piano non autonomo, che può essere trasformato in un sistema autonomo tridimensionale. Viene descritto il comportamento globale di quest'ultimo nei due casi di rendimenti crescenti o decrescenti. Si dimostra, in particolare, l'assenza di attrattori economicamente significativi ed il diverso carattere delle orbite: mentre, se i rendimenti sono crescenti, le traiettorie convergono asintoticamente ad un punto singolare dove l'economia muore, nel caso opposto le traiettorie sono illimitate e spiraleggiano intomo ad una retta che ha la direzione dell'assek (la variabile di stato che rappresenta lo stock di capitale).

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This paper relates to the activities of the M.P.I. Group Dinamiche Non-Lineari nelle Scienze Economiche e Sociali.     

Effective participative decision making: A joint responsibility for success

Much of the current research on participative decision making focuses on the increasing need for broad-based decision-making systems, on the different outcomes associated with different forms of participation, or on the problems associated with poorly managed participative decision-making systems. This article considers the responsibilities of employees who participate in organizational decision making and the responsibilities of employers who expect to share decision-making tasks. A Bill of Responsibilities for Employees and a Bill of Responsibilities for Employers are presented. Pitfalls associated with neglecting these responsibilities are discussed.     

On monotone optimal decision rules and the stay-on-a-winner rule for the two-armed bandit

Summary Consider the following optimization problem: Find a decision rule such thatw(x, (x))=max _a w(x, a) for allx under the constraint (x)D (x). We give conditions for the existence of monotone optimal decision rules . The term monotone is used in a general sense. The well-known stay-on-a-winner rules for the two-armed bandit can be characterized as monotone decision rules by including the stage number intox and using a special ordering onx. This enables us to give simple conditions for the existence of optimal rules that are stay-on-a-winner rules. We extend results ofBerry andKalin/Theodorescu to the case of dependent arms.     

The economic transformation of Eastern Europe: the case of Poland

This article identifies the main features of Poland's radical transition to capitalism-stabilization program, trade liberalization, and privatization reform. The shock therapy adopted by Poland in 1991 is presented as the most effective approach, though not without political risk. In fact, the major threat to Poland's transition process is the emergence of well organized interest groups putting increasing demand on the government to relax financial restrictions and re-open large-scale subsidization. These political pressures have already caused a slowdown in the privatization program, so that there is a possibility of the renewal of rapid inflation. Several methods for accelerated privatization, including the distribution of vouchers and setting up investment funds to manage portfolios of shares, are discussed in detail.     

RAM: A Range Adjusted Measure of Inefficiency for Use with Additive Models,and Relations to Other Models and Measures in DEA

Generalized Efficiency Measures (GEMS) for use in DEA are developed and analyzed in a context of differing models where they might be employed. The additive model of DEA is accorded a central role and developed in association with a new measure of efficiency referred to as RAM (Range Adjusted Measure). The need for separately treating input oriented and output oriented approaches to efficient measurement is eliminated because additive models effect their evaluations by maximizing distance from the efficient frontier (in ₁, or weighted ₁, measure) and thereby simultaneously maximize outputs and minimize inputs. Contacts with other models and approaches are maintained with theorems and accompanying proofs to ensure the validity of the thus identified relations. New criteria are supplied, both managerial and mathematical, for evaluating proposed measures. The concept of approximating models is used to further extend these possibilities. The focus of the paper is on the physical aspects of performance involved in technical and mix inefficiencies. However, an Appendix shows how overall, allocative and technical inefficiencies may be incorporated in additive models.     

Confronto fra eventi condizionati di probabilità nulla nell'inferenza statistica Bayesiana

Dopo aver introdotto delle operazioni logiche fra eventicondizionati (che estendono opportunamente quelle usuali fra eventi), si definisce il concetto di iperprobabilità condizionata Si può così dare una interpretazione significativa della pseudodensità condizionata, introdotta da R. Scozzafava nell'inferenza statistica bayesiana.

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By a suitable extension of the usual algebra of events, logical operations forconditional events are introduced. This leads to a definition of conditional iperprobability, which is the natural tool for a sensible interpretation of the concept of conditional pseudodensity, introduced by R. Scozzafava in Bayesian statistical inference.

     

A numerical representation of semiorders on a countable set

Let be a semiorder on a countable setX and letx⁰ y if and only if either there existsx withxxy or there existsx withxxy. Then ⁰ is a preference relation with transitive indifference, which can be represented by a utility functionf of the usual sort. It is well known that is represented by a pair of real-valued functionsu, v, in the sense thatxy if and only ifu(x)>v(y). We prove that there exists a pair of functionsu, v, representing , such thatu+v is the utility function which represents in the usual sense. Moreover it is easily seen that, for such a pair of functionsu, v, we havex⁰ y if and only if eitheru(x)>u(y) or (u(x)=u(y) andv(x)>v(y)).

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Sommario Consideriamo unsemiordine su un insiemeX numerabile e poniamox⁰ y se e solo se esistex tale chexxy, oppure esistex tale chexxy. In questo caso ⁰ è unordine debole, che può essere rappresentato da una funzione di utilitàf nel senso usuale. D'altra parte è rappresentato da una coppia di funzioniu, v, nel senso chexy se e solo seu(x)>v(y). In questo lavoro si prova che ammette una rappresentazioneu, v tale chex⁰ y se e solo seu(x)+v(x)>u(y)+v(y). Si dimostra altresì che, con riguardo ad una siffatta rappresentazioneu, v di , riescex⁰ y se e solo seu(x)>u(y) oppure (u(x)=u(y) ed anchev(x)>v(y)).

     

An alternative direct proof of Gibbard’s random dictatorship theorem

We present an alternative proof of the Gibbards random dictatorship theorem with ex post Pareto optimality. Gibbard(1977) showed that when the number of alternatives is finite and larger than two, and individual preferences are linear (strict), a strategy-proof decision scheme (a probabilistic analogue of a social choice function or a voting rule) is a convex combination of decision schemes which are, in his terms, either unilateral or duple. As a corollary of this theorem (credited to H. Sonnenschein) he showed that a decision scheme which is strategy-proof and satisfies ex post Pareto optimality is randomly dictatorial. We call this corollary the Gibbards random dictatorship theorem. We present a proof of this theorem which is direct and follows closely the original Gibbards approach. Focusing attention to the case with ex post Pareto optimality our proof is more simple and intuitive than the original Gibbards proof.Received: 15 October 2001, Accepted: 23 May 2003, JEL Classification: D71, D72Yasuhito Tanaka: The author is grateful to an anonymous referee and the Associate editor of this journal for very helpful comments and suggestions. And this research has been supported by a grant from the Zengin Foundation for Studies on Economics and Finance in Japan.     

Maximal asymptotic power and efficiency of two-sample tests based on generalized U-Statistics

In this article a systematic study is given of the asymptotic behavior of two-sample tests based on U-Statistics with arbitrary antisymmetric kernels . Besides the investigation under the hypothesis and under fixed alternatives we determine the local power as a function of as well as its maximizing value _opt. Moreover formulas for the asymptotic relative efficiency ARE(₂,₁) of the ₂-test with respect to the ₁-test are derived. It turns out that _opt also yields the most efficient test in the sense that ARE(_opt,)1 for all (admissible) kernels .     

Una funzione ordinale di benessere sociale

In questo lavoro trattiamo il problema di come amalgamare preferenze di individui in una preferenza sociale in relazione a certe alternative determinando una preferenza sociale che soddisfa i due Assiomi e le Condizioni 1,4,5 di Arrow.

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Summary In this paper we deal with the problem of how to amalgamate individual preferences to form one social preference in relation to certain alternatives determining a social preference satisfying the 2 Axioms and the 1, 4, 5 Conditions of Arrow.

     

Studio deglieffetti di due sistemi di tassazione progressiva in un modello di utilita' attesa a due periodi

Dopo avere introdotto due sistemi di tassazione progressiva in un modello di utilità attesa a due periodi, si analizzano gli effetti che un tale tipo di tassazione ha sui consumi e sugli investimenti in beni a rischio.

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Summary Two systems of progressive taxation are introduced in a two-period expected utility model; then the effects that such a kind of taxation has on the consumption and on the investment in risky assets are analyzed.

     

Social identity,inequality, and conflict: correction and extension

This paper corrects and extends the analysis in Social Identity, Inequality, and Conflict by James Robinson (Economics of Governance, 2(1), 2001). For conflict along class lines, Robinson finds the total impact of mobility on conflict to be ambiguous. Contrary to his result, I show that, under his assumptions, the effect of social mobility on class conflict is unambiguous. Higher mobility always decreases conflict. In my extension to Robinsons model, I explore mobilitys impact on class conflict in a society where the tax rate is not fixed. I demonstrate that if the tax rate is proportional to the population of the group in power relative to the total population of the society, then the effects of social mobility on class conflict are indeed ambiguous.Submitted: February 2002, Accepted: July 2003,I am grateful to an anonymous referee and Amihai Glazer for their comments. I would also like to thank Herschel Grossman for his help along the way.     

Technical Inefficiency Effects Among Paddy Farmers in the Villages of the ‘Office du Niger’, Mali,West Africa

A stochastic frontier production function incorporating a model for technical inefficiency effects (Battese and Coelli, 1995) is applied to field data on paddy farmers from 29 villages in the Office du Niger in Mali. Four conventional factors (land, labor, fertilizer and machinery) are considered as inputs of production. The technical inefficiency effects in the stochastic frontier were related to firm-specific variables, institutional factors, social organisation, ecological considerations and health factors. Data were obtained from an economic survey conducted during two consecutive agricultural seasons (1989 and 1990) on 844 farms of the Office du Niger. The null hypothesis of the absence of technical inefficiency effects was rejected. A supportive institutional environment and a coherent organisation of land use were the best correlates of technically efficiency. The social environment was also found to contribute to technical efficiency of the paddy farmers: within the village, the greater the degree of ethnic cohesion, the greater the efficiency of the farmers. Health status of households had an effect in that healthy families tended to be more technically efficient than unhealthy ones. Farmers with more extensive sorghum cultivation were less efficient as paddy farmers. These results may help agricultural policy makers formulate strategies. Technical efficiency may be improved by intensifying agricultural training regarding one specific crop and, through the control of parasitic diseases which place a burden on family households.     

“Good Cause Beliefs” in an “At-Will World”? A Focused Investigation of Psychological Versus Legal Contracts

This study assesses the psychological contracts of a group of at-will employees and compares their relevant psychological contract beliefs with the terms of the controlling legal employment contract. In addition, we test specific hypotheses regarding the relationship between employers formal job security policy (employment at-will vs. good cause protection, and employee personal characteristics; equity sensitivity, organizational tenure) to 2 focal psychological contract beliefs (the employers obligation to have a good reason to discharge the employee, and the employees reciprocal obligation to have a good reason to leave his/her employer). These issues are investigated using survey data sampled from 15 diverse U.S. organizations, and independently collected information regarding organizations job security policies. The results provide evidence of a widely shared psychological contract belief that, despite explicit at-will policies, U.S. employers are highly obligated to have a good reason to discharge employees. Further, personal characteristics are more strongly related to the focal psychological contract beliefs than employer job security policies. The theoretical contribution of the study and its practical implications are discussed.     

Minimal efficiency of designs under the class of orthogonally invariant information criteria

Consider the linear regression model with uncorrelated errors and an experimental design . In the article, we address the problem of calculating the minimal efficiency of with respect to the class of orthogonally invariant information criteria, containing all Kiefers criteria of _p-optimality, among others. We show that the -minimal efficiency of is equal to the minimal efficiency of with respect to a finite class of criteria which generalize the criterion of E-optimality. We also formulate conditions under which a design is maximin efficient, i.e. the most efficiency-stable for criteria from . To illustrate the results, we calculated the -minimal efficiency of _p (in particular D, A and E) optimal designs for polynomial regression on [–1,1] up to degree 4. Moreover, for the quadratic model we explicitly constructed the -maximin efficient design.Acknowledgement. The author would like to thank prof. Pázman as well as an anonymous referee for useful and inspiring comments on earlier versions of this article.Supported by: VEGA grant of the Slovak Agency No. 1/0264/03     

Sulla convergenza di un algoritmo di direzioni ammissibili per problemi di ottimo a vincoli lineari con funzione oggetto convessa non differenziabile

Se, essendof la funzione obiettivo del problema, {x ^k } e {f(x ^k )} sono le successioni delle approssimazioni rispettivamente di una soluzione ottimax ^* e dell' ottimof(x ^*) generate da un noto algoritmo di direzioni ammissibili a parametri antizigzag _k , mostriamo che per avere (a) lim _k f(x ^*)=f(x ^*) basta assumere lim _{k k} =0. Inoltre, ove si assuma in più la stretta convessità dif, si ha anche (b) lim _k x ^k =x ^*. Da quest'ultima condizione deriviamo infine specifiche ipotesi, in ordine alla (b), per il caso particolare del problema di trasporto stocastico.

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Summary The aim of the present paper is to analyze, without differentiability of the objective functionf, the convergence of a known «feasible directions» algorithm for constrained optimization problems having the constraints linear [8], 6.5.2.In these circumstances (i.e. iff is not differentiable) one must, almost in general, verify some preliminary conditions to obtain convergence [4]. Nevertheless, this work is not always easy to accomplish particularly in absence of differentiability.Here, we establish that under the convexity assumption forf, the only condition lim _{k k} =0, where the _k are the antizigzag parameters, suffices to obtain the convergence of the algorithm, i.e. lim _k f(x ^k )=opt., thex ^k being the approximate solutions to problem. The proof is obtained by application of the Th. 24.5, [6]. Successively, we consider the question if one has also the convergence of {x ^k } to optimal solution. By using now the Cor. 27.2.2, [6], we establish, for this purpose, that under an additional general qualification forf — precisely the strict convexity — the convergence of {x ^k } is also stated. Finally, we examine the above property for the stochastic transportation problem [1] for which we indicate special conditions in order to verify the latter convergence property.

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pervenuto il 28-4-82     

A note on optimum spacing of observations from a continuous time simple Markov process

Summary Assume thatX() is a continuous time simple Markov process with a parameter . The problem is to choose observation points ₀ < ₁ <...<_T which provide with the maximum possible information on . Suppose that the observation points are equally spaced, that is, fort=1, ...,T, T, ;_t–_t–1 is constant. Then the optimum value fors is obtained.