Structural breaks and long-run trends in commodity prices

The oil shocks of the 1970s, which quadrupled the price of petroleum, marked the end of an abnormal period of price stability and renewed interest in predicting the evolution of commodity prices. But most subsequent studies have focused on the short-run effects of price fluctuations, mainly because they greatly affect the foreign trade of developing countries. Sophisticated compensation mechanisms, such as commodity funds, have been introduced to counterbalance the transitory effects of price shocks. But the long-term evolution of prices also affects policy design and development strategies and may have a more important role in fostering long-run growth. The evidence presented by Prebisch (1950) and Singer (1950) of a secular negative trend in the price of commodities in 1870-1945 implies an increasingly weak position for developing countries relative to industrial economies. This hypothesis by Prebisch and Singer has been strongly debated, both theoretically and empirically, during the past four decades. Using recent advances in econometric theory, the authors analyze the long-run dynamics of the price of the 24 most-traded commodities in 1900-92. The method they use tests for nonstationarity (unit roots) in the series with a technique that allows structural breaks to be endogenously determined. The results show that 15 of the 24 commodity prices present negative trends, six are trendless, and three exhibit positive trends. Thus, the Prebisch-Singer hypothesis though not universal, holds for most commodities. This evidence rejects, to some extent, previous evidence by Cuddington (1992) and others. The authors extend the econometric analysis to determine the persistence of shocks to commodity prices. Knowledge of the persistence of shocks is important when designing counterbalancing policies such as commodity funds. The authors use a nonparametric estimator of persistence (the multiple variance ratio) and find that 19 of the 24 commodity prices present persistence levels substantially lower than previous estimates. This evidence suggests that there may be substantial room for stabilization and price support mechanisms for most commodities.Scientific Research&Science Parks,Environmental Economics&Policies,Economic Theory&Research,Markets and Market Access,Commodities,Environmental Economics&Policies,Economic Theory&Research,Markets and Market Access,Access to Markets,Commodities

Hot spots and the hollowness of proton-proton interactions at high energies

We present a dynamical explanation of the hollowness effect observed in proton-proton scattering at $\sqrt s\!=\!7$ TeV. This phenomenon, not observed at lower energies, consists in a depletion of the inelasticity density at zero impact parameter of the collision. Our analysis is based on three main ingredients: we rely gluonic hot spots inside the proton as effective degrees of freedom for the description of the scattering process. Next we assume that some non-trivial correlation between the transverse positions of the hot spots inside the proton exists. Finally we build the scattering amplitude from a multiple scattering, Glauber-like series of collisions between hot spots. In our approach, the onset of the hollowness effect is naturally explained as due to the diffusion or growth of the hot spots in the transverse plane with increasing collision energy.Comment: 4 pages, 3 figure

Moratín y el drama burgués: el teatro de lo privado

En este trabajo se exponen las razones que llevan a considerar el teatro neoclásico de Moratín como un teatro de lo privado, su innegable relación con la recién aparecida burguesía y cómo Moratín supone un solitario punto de ruptura con la tendencia literaria que le precede y con la que le sucederá

Shumpall, mitología y erotismo en la poesía de Roxana Miranda Rupailaf / Shumpall, mythology and eroticism in the poetry of Roxana Miranda Rupailaf,

RESUMEN: La poesía etnocultural de los últimos años del siglo XX evidencia una escritura motivada por la ascendencia indígena, pero también una ascendencia mestiza dado que ambas conviven en una sociedad ampliamente multicultural como es el sur de Chile. La obra de Miranda Rupailaf se caracteriza por la presencia de variados imaginarios rurales-costeros del sur de Chile que son incorporados en su poética por medio del mito del Shumpall. Este ha de proteger el agua de ríos, lagos y lagunas, junto con la capacidad de abastecer de alimentos a la población. Todo esto es relatado por medio del mito y el nutram que corresponde al relato histórico en clave poética, como evidencia de la conciencia de etnia de la autora, tras someter el texto a la clásica pregunta de Spivak, ¿Puede hablar el subalterno?Palabras Clave: Poesía etnocultural, mitología mapuche, imaginario y erotismo.ABSTRACT: Ethnocultural poetry of the last years of the 20th century shows a script driven indigenous ancestry, but also mestizo since both coexist in a widely multicultural society at the south of Chile. The work of Miranda Rupailaf is characterized by the presence of various rural-coastal imageries that are incorporated in their language by means of the mapuche mith, the Shumpall. This is to protect water from rivers, lakes and ponds, along with the ability to provide food for the population. All this is told through myth and nutram corresponding to key historical narrative in poetry, as evidence of consciousness of ethnicity of the author, after subjecting the classic question of the text Spivak, Can the subaltern speak?Key Words: Mythology, imagination, eroticism, Mapuch

Derechos de propiedad y externalidades en las llanuras de inundación de la Cuenca Alta del rio Aburrá (2000-2015): un caso sobre detonantes de tensiones y conflictos socio ambientales

La vulneración de instituciones formales como las Normas de usos del suelo, las cuales delimitan los derechos de propiedad, y los instrumentos de planificación como el plan BIO2030, POMCA y PBOT municipales, ha sido fuente de generación de externalidades negativas que desatan a su vez tensiones y conflictos socio ambientales entre actores públicos, privados y comunitarios asentados en la cuenca -- Con la ocupación irregular de las áreas de retiro y llanuras de inundación –ARLLIRA- en la cuenca alta del río Aburrá, para fines industriales, comerciales y vivienda desapareció la función de regulación natural de la cantidad y velocidad del caudal del río; entendida esta, como un servicio público “puro” de carácter ambiental del que ninguna persona o colectivo puede ser excluido o rivalizar por est

Influence of Population Income and Climate on Air Pollution in Cities due to Buildings: The Case of Spain

Article number 1051Half of the world’s population lives in cities. In addition, more than 40% of greenhouse gas emissions are produced in buildings in the residential and tertiary sectors. Therefore, cities, and in particular their buildings, have a great influence on these emissions. In fact, they are reflected in several of the United Nations’ Sustainable Development Goals. Any measure taken to reach these goals has a significant impact from the point of view of reducing greenhouse gases. An understanding of these goals is the basis of greenhouse gas mitigation. This work analyzed the CO2 emissions from the buildings in cities as a function of the economic income of their inhabitants. For this, databases published by official sources were used. The origins of the CO2 are usually emitted by buildings were analyzed—electrical and thermal, in the form of natural gas. Another variable that influences these emissions is climate. To study only the income variable, the influence of climate has been eliminated. Also, to facilitate analysis, an index has been introduced. As an example of application of the proposed methodology, Spanish cities with more than 50,000 inhabitants were studied. The analysis was carried out by household and by inhabitant. The results showed the following: the higher the income of the citizens, the higher the total and thermal emissions; thermal consumption is elastic, while electrical consumption is inelastic; emissions of electrical origin are almost constant; emissions from electrical energy are greater than those from thermal energy; as income increases, the ratio between emissions of electrical and thermal origin decreases

Statistical Depth by Reflections

ABSTRACT: We define a two-dimensional statistical depth function and study two important aspects of it: its robustness and computability. We begin by formally proving that the function is, indeed, a statistical depth function. To achieve this, we introduce a new notion of symmetry for distributions in Rp . We study the robustness through the concept of breakdown point. In terms of computability, we provide an implementable algorithm to calculate the depth contours with temporal complexity Θ(n²) and spatial complexity Θ(n), where n is the size of the data set. As an application of the proposed depth function, we provide a hypothesis test for the independence of two absolutely continuous variablesRESUMEN: Definimos una función de profundidad estadística bi-dimensional y estudiamos dos aspectos importantes de la misma: la robustez y la computabilidad. Comenzamos probando formalmente que la función es, de hecho, una función de profundidad estadística. Para conseguirlo, introducimos una nueva noción de simetría para distribuciones en Rp . Estudiamos la robustez a través del concepto de breakdown point. En cuanto a la computabilidad, proporcionamos un algoritmo implementable para calcular los contornos de profundidad con complejidad temporal Θ(n²) y complejidad espacial Θ(n), siendo n el tamaño del conjunto de datos. Como aplicación de la función de profundidad propuesta, proporcionamos un contraste de hipótesis para la independencia de dos variables absolutamente continuas.Grado en Matemática

Building Personal Learning Environments by using and mixing ICT tools in a professional way

This paper reports on a teaching experience of the introduction of ICT to higher education students in a complementary professional approach and a Personal Learning Environment (PLE) development approach, as well as a naturalistic study based on this experience. The central focus of this methodology was the use of hands-on sessions to introduce students to somespecific ICT tools, and exploring the building process of an awareness abouttheir Personal Learning environments.In terms of learning, we confirmed that students very much appreciate new ways of developing their tasks and their course work. Even when the great majority of students associates learning with acquiring only information and some of them associate learning with memorizing.In terms of Technology, after this experience we can conclude that students,when arriving at university, have no experience –even knowledge- in the useof ICT tools. In addition, students from the first year of the degree don’t thinkthey use Web 2.0 (awareness), and even more, they don’t believe that theycan use ICT tools for learning, even if they actually do. They value, usefultools which help them to plan their tasks, save time, simplify complicatedtasks and, definitively, have fun; but also they specially value the ICT toolsthey discovered, seeing opportunities for Independency, collaboration, self importance in the learning process.The vast majority of students have a basic perception of their PLE. Few ofthem don’t relate tools with themselves but with their tasks, and only some ofthem go one step further by establishing more complex relationships betweentools, contents, tasks and themselves enriching each other.This paper reports on a teaching experience of the introduction of ICT to higher education students in a complementary professional approach and a Personal Learning Environment (PLE) development approach, as well as a naturalistic study based on this experience. The central focus of this methodology was the use of hands-on sessions to introduce students to somespecific ICT tools, and exploring the building process of an awareness abouttheir Personal Learning environments.In terms of learning, we confirmed that students very much appreciate newways of developing their tasks and their course work. Even when the greatmajority of students associates learning with acquiring only information andsome of them associate learning with memorizing.In terms of Technology, after this experience we can conclude that students,when arriving at university, have no experience -even knowledge- in the useof ICT tools. In addition, students from the first year of the degree don't thinkthey use Web 2.0 (awareness), and even more, they don't believe that theycan use ICT tools for learning, even if they actually do. They value, usefultools which help them to plan their tasks, save time, simplify complicatedtasks and, definitively, have fun; but also they specially value the ICT toolsthey discovered, seeing opportunities for Independency, collaboration, self importance in the learning process.The vast majority of students have a basic perception of their PLE. Few ofthem don't relate tools with themselves but with their tasks, and only some ofthem go one step further by establishing more complex relationships betweentools, contents, tasks and themselves enriching each other