Top-<Emphasis Type="Italic">k</Emphasis>-lists

Top-k-lists are introduced as sequences of k-dimensional random vectors with ordered components being k largest observations from a sequence of independent identically distributed random variables. Such lists changing in time are natural stochastic models of ranking tables which appear in many situations in real life, when one wants to keep a track of several best results in a given field. Here we study basic properties of top-k-lists as joint distributions, conditional structures, representations, driving examples of top-k-lists from exponential and uniform distributions, asymptotics and a relation to generalized order statistics.     

Volatility in asset prices and long-run wealth effect estimates

We argue that the equation commonly used in the estimation of the wealth effect on consumption might be unsuitable for that purpose. In particular, if the usual assumptions are employed, the derivation of the equation implies that the wealth effect is indeterminate. Furthermore, it implies that the estimate of the wealth effect should decrease when asset wealth volatility increases. Estimation of a Markov-switching model of the usual long-run aggregate consumption equation provides evidence favourable to the indeterminacy hypothesis.     

The Strategic Social Map of a Nongovernmental Organization

Currently, the traditional states-nation, as far as their social commitments are concerned, are giving way to the nongovernmental organizations (NGO). These organizations have a mission, strategy, and goals different from those organizations looking simply for profits. Nevertheless, NGOs are concerned about using management and information systems at least as good as those used by private companies. Organizations try to develop a social strategy taking their social responsibility as starting point. In this paper, the authors describe how to fix the organization mission, its strategy and goals, and also how to make its action map. A strategy proposal will be described, as well as the way on how to put it into practice. The main goals of this paper is to describe the mission, strategy, and goals of the organization; design its strategic social map; fix the limits of the organization's action; apply the theoretical model to a NGO; and design an information model in order to manage the strategic development. The authors would like to express their gratitude to M. Dolors Celma Benaiges, lecturer at the Escola Universitària del Maresme, Universitat Pompeu Fabra, for her assistance reviewing and translating the paper.     

Optimal risk-sharing with effort and project choice

We consider first-best risk-sharing problems in which “the agent” can control both the drift (effort choice) and the volatility of the underlying process (project selection). In a model of delegated portfolio management, it is optimal to compensate the manager with an option-type payoff, where the functional form of the option is obtained as a solution to an ordinary differential equation. In the general case, the optimal contract is a fixed point of a functional that connects the agent's and the principal's maximization problems. We apply martingale/duality methods familiar from optimal consumption-investment problems.     

Copula‐Based Formulas to Estimate Unexpected Credit Losses (The Future of Basel Accords?)

The model used to estimate the capital required to cover unexpected credit losses in financial institutions (Basel II) has some drawbacks that reduce its ability to capture potential joint extreme losses in downturns. This paper suggests an alternative approach based on Copula Theory to overcome such flaws. Similarly to Basel II, the suggested model assumes that defaults are driven by a latent variable which varies as a response to an unobserved factor. On the other hand, the use of copulas allows the identification of asymmetric dependence between defaults which has been registered in the literature. As an example, a specific copula family (Clayton) is adopted to represent the association between the latent variables and a formula to estimate potential unexpected losses at a certain level of confidence is derived. Simulations reveal that, in most of the cases, the alternative model outperforms Basel II for portfolios with right‐tail‐dependent probabilities of default (supposedly, a good representation for real loan portfolios).     

Evolving Aspirations and Cooperation

A 2×2 game is played repeatedly by two satisficing players. The game considered includes the Prisoner's Dilemma, as well as games of coordination and common interest. Each player has anaspirationat each date, and takes an action. The action is switched at the subsequent period only if the achieved payoff falls below aspirations; the switching probability depends on the shortfall. Aspirations are periodically updated according to payoff experience, but are occasionally subject to trembles. For sufficiently slow updating of aspirations and small tremble probability, it is shown that both players must ultimately cooperate most of the time.Journal of Economic LiteratureClassification Numbers C72, D83.     

Persistence,Long Memory,and Unit Roots in Commodity Prices

This article investigates the degree of persistence in several weekly and monthly agricultural prices (corn, soybeans, barrow and gilts, and milk) using long memory (fractional integration) techniques. The results indicate mean reversion (i.e., orders of integration smaller than one) in some of the agricultural prices like corn, milk, and barrow and gilts when the disturbances are autocorrelated. Further, we examine the stability across time in the degree of dependence, and the results indicate that the fractional differencing parameters have not remained constant across time. When we take into account a structural break we find that during the first subsamples, the series are stationary though highly persistent, with orders of integration close to 0 and with large autoregressive coefficients. However, for the periods after the break, the series seem to be nonstationary I(1). Dans le présent article, nous avons étudié le degré de persistance des prix hebdomadaires et mensuels de plusieurs produits agricoles (maïs, soja, castrats et cochettes, lait) à l’aide de tests de mémoire longue (intégration fractionnaire). Nos résultats indiquent une stationnarité (c.‐à.‐d. des ordres d’intégration inférieurs à un) des prix de certains produits agricoles, tels que le maïs, le lait, les castrats et cochettes, lorsque les perturbations sont autocorrélées. Nous avons également étudié la stabilité du degré de dépendance à travers le temps, et nos résultats indiquent que les paramètres de différenciation fractionnaire ne sont pas demeurés constants. Lorsque nous avons tenu compte d’une rupture structurelle, nous avons trouvé que dans les premiers sous‐échantillons, les séries étaient stationnaires quoique très persistantes, avec des ordres d’intégration près de 0 et d’importants coefficients d’autorégression. Dans le cas des périodes suivant la rupture, les séries semblaient non stationnaires I(1).     

Volatility transmission along the money market yield curve

Volatility Transmission along the Money Market Yield Curve. - The authors model the volatility of money market interest rates — and the transmission of volatility - along the money market yield curve in the UK, Germany, France and Spain. They find a significant volatility transmission from overnight to longer-term money market rates in France, Spain and the U.K. They also find that the countries with lower (higher) reserve requirements tend to have higher (lower) interbank interest rate volatility. However, reserve requirements generate a perverse seasonal effect at the end of the maintenance period.     

Designing minimum-cost recycling collection networks with required throughput

The problem of designing minimum-cost recycling networks with required throughput is a subset of the broader class of facility location problems in which the recycler wishes to determine the optimal number and location of receiving centers as well as the correct financial incentive to be offered in order to stimulate collection of used or unrecoverable products to a degree required for regulatory reasons or otherwise. This paper presents a conceptual framework, an analytical model, and a three-stage algorithmic solution for this problem. An illustrative case study in the recycling of unrecoverable tires in southern states of Brazil is presented.