Nonfractional Memory: Filtering, Antipersistence, and Forecasting

The fractional difference operator remains to be the most popular mechanism to generate long memory due to the existence of efficient algorithms for their simulation and forecasting. Nonetheless, there is no theoretical argument linking the fractional difference operator with the presence of long memory in real data. In this regard, one of the most predominant theoretical explanations for the presence of long memory is cross-sectional aggregation of persistent micro units. Yet, the type of processes obtained by cross-sectional aggregation differs from the one due to fractional differencing. Thus, this paper develops fast algorithms to generate and forecast long memory by cross-sectional aggregation. Moreover, it is shown that the antipersistent phenomenon that arises for negative degrees of memory in the fractional difference literature is not present for cross-sectionally aggregated processes. Pointedly, while the autocorrelations for the fractional difference operator are negative for negative degrees of memory by construction, this restriction does not apply to the cross-sectional aggregated scheme. We show that this has implications for long memory tests in the frequency domain, which will be misspecified for cross-sectionally aggregated processes with negative degrees of memory. Finally, we assess the forecast performance of high-order $AR$ and $ARFIMA$ models when the long memory series are generated by cross-sectional aggregation. Our results are of interest to practitioners developing forecasts of long memory variables like inflation, volatility, and climate data, where aggregation may be the source of long memory

Regulación de la natalidad y violencia

Ours is a period marked by violence, and, most important, it is no stranger either to reproduction. In arder to clarify concepts, by violence we mean, formally speaking, any interference or action by an external agent on a situation, structure, phenomenon or process with the object of nullifying it or of changing either its meaning (by deviation) or its intensity (by slowing it down or by accelerating it). In this sense violence is not intrinsically illicit. One must distinguish between violen ce and violation. After a short study of the concepts of law, order and justiee in the fundamental works of the principal Natural Law investigators of the present day, the author arrives at the conclusion that the genuine meaning of the term violation is any attempt against a principie of order, either directly of by undermining any of the other elements of order, be they real or related. The human vocation of dominion over Nature, insofar as Man is a superior being, should not be thought of in absolute terms: it consists in being responsible for the conservation, reproduction, development and perfection of all creatures that tend towards their completeness according to individual ends which integrate themselves progressively towards one general goal. For this mission, which in general terms is called culture, man has a certain autonomy, but not full independence; and the degree of autonomy is much more reduced with respect to his own species than in the case of inferior creatures. Man's capacity and his science can suffer desviations. Insofar as biology is concerned, these presentday desviations are serious and well known. The attempt against the physical and natural order, especially in the animal sphere, is widespread and threatens to obtain firm footing. In this sense, we see that violence is being used, not in its I awfu I (and at times necessary) meaning of correction, of restoration of order, but as its violation. The author has confined his examination of the problem to the question of human population: he discusses three fundamental aspects: prostitution 01 the biological culture, separation 01 erotic appetite and reproduction, conflict between individual rights and social interests. The «scientific» attempts against the reproductive processes, including those previous to gametogenesis as well as the actual fertilization, are classified together under the heading of contraception. Both aspects are studied extensively and the author concludes that they are unlawful according to the Natural Law. The arguments of the proponents of contraception are studied and compared with those of their opponents, and special importance is given to biological and philosophical considerations; the conclusion is that no jurist with proper regard for legal considerations can accept theories that contradict authority and that can well be classified as setting precedents, especially when the matter is undergoing research. The author examines the various present-day aspects of the -sexual revolution » as a key to explaining the many postulates and tendencies as well as the possible collision between individual rights and group interests. The question of continence and Chastity are next examined. The discussion of human reproduction oscillates today between the two poles of «biological» and «scientific» arguments, with considerations regarding the meaning and limitations of these expressions and their consequences and applications. This is followed by a short analysis of the pragmatic attitude adopted by various politicians in their approach to these questions. After sorne short reflections on the limitations of human freedom implied by the present attitude towards the sexual revolution, the author makes a final conclusion in which he refers to self-control

The mean frequency of recurrence of in-time-multidimensional events for drought analyses

International audienceDroughts are related with prolonged periods when moisture is significantly below normal values. Drought indices attempt to scale the main drought features to facilitate comparisons. Numerous indices are found in the literature based on different drought features. Many of them were created for particular places and specific objectives, and therefore not suitable to generalize the results. However, there have been attempts to develop a general index, which would provide full characterization of drought events. Two of the most well known are the Palmer Drought Severity Index (PDSI) and the Standard Precipitation Index (SPI). Each one has particular advantages and disadvantages. Still neither of them or any other includes a full representation of droughts in a single value index, being useful for all general application. The fact that droughts have a random nature prescribes the statistical theory for the foundation of a complete and generic index, which would meet this goal. In this work, a procedure that allows a complete statistical characterization of drought events is presented. Droughts are characterized, from a statistical point of view, based both on the deviation from a normal regime and persistence. The events are represented as multivariate ones, whose dimensionality depends on the duration. Equal duration events are discriminated through their deviations from normality. The mean frequency of recurrence (MFR) is theoretically derived for such multivariate events, and it is used to scale such deviations. Therefore, events with different dimensionalities can be compared on a common dimension of interest, the MFR. This may be used as a drought index for drought characterization, both for analyzing historical events and monitoring current conditions. It may also be applied to analyze precipitation, streamflows and other hydroclimatic records. Its statistical nature and its general conception support its universality. Results may be applied not only to drought analysis, but also to analyze other random natural hazards. Applications of the procedure for drought analysis in Texas (USA) and in Gibraltar (Iberian Peninsula) are made and compared with PDSI and SPI results. The MFR applied over drought analysis allows the representation of the main drought characteristics in a single value, based on the statistical feature of the phenomenon, and scaled on the mean frequency of recurrence

A Historical Account of Difference: A Comparative History of the Literary Cultures of Latin America

In his article A Historical Account of Difference: A Comparative History of the Literary Cultures of Latin America, Mario J. Valdés addresses the well-recognized limitations of literary history as historical research. Valdés outlines the theoretical thinking that has guided the editors of The Oxford Comparative History of Latin American Literary Cultures to plan, organize, and complete the first history of literary culture of Latin America. The project is comparative, recognizing the radical diversity of the continent while at the same time it is an open-ended history that informs but does not attempt to provide a totalizing account of more than five hundred years of cultural development among the heterogeneous entities that make up Latin America. Valdés begins by considering the paradox of literary history, he then suggests ways that literary history can be shaped by the work of Michel Foucault, and he proposes a framework for a hermeneutics of literary history. Valdés also considers the challenges that face the literary historian whose work now includes cultural history. All of these considerations are then placed within the context of an effort to create a literary and cultural history of Latin America