Caracterización selvícola de las masas monoespecíficas de pino laricio en Cataluña

En el presente trabajo se ha abordado, a partir de la información suministrada por el Segundo Inventario Forestal Nacional, la caracterización de las masas monoespecíficas de pino laricio en Cataluña (NE de España), formalizándola en una tipología de enfoque silvogenético. Basándose en los resultados obtenidos del análisis factorial realizado sobre variables dasométricas, los categoremas de la tipología se articularon sobre aspectos concernientes a la distribución diamétrica y espesura del rodal, identificándose nueve tipos. El carácter irregularizado, presente en cinco de ellos aunque con rasgos diferentes, se examinó a través de la distribución de Weibull truncada. La tipología, que se maneja computando tan sólo el nivel de regenerado y los diámetros de los pies inventariables, contempla los distintos estadios evolutivos y permite diagnosticar situaciones comprometidas en cuanto a la persistencia de la masa, bien causadas por deficientes estados de espesura o por falta de regenerado.

The Significance of Business Exit for Future Entrepreneurial Activity

Purpose: The purpose of this paper is to analyse the impact of business exits on future dimensions of entrepreneurial activity at the macroeconomic level. Design/methodology/approach: This research uses the Global Entrepreneurship Monitor (GEM) data for 41 countries and the Generalized Method of Moments (GMM) to carry out the analysis. The paper differentiates the effect of the two components of total entrepreneurial activity, and the two motivations for it – opportunity and necessity entrepreneurship. Findings: The results presented here show a positive and significant effect of the coefficient associated with exits in all models. This means that the levels of entrepreneurial activity exceed business exits. The robustness of the models are tested, including other variables such as the fear of failure, the Gross Domestic Product, role models, entrepreneurial skills and the unemployment variables. The main hypothesis which stated that at national level business exits imply greater rates of opportunity-driven entrepreneurship is corroborated. Originality/value: One would expect that unemployment rates would imply higher levels of necessity entrepreneurship. However, results show that unemployment rates do in fact favour opportunity entrepreneurship levels. This could be due to those government policies that are aimed at promoting entrepreneurship through the capitalization of unemployment to be totally invested in a new start-up. To the best of our knowledge, this is the first panel data study to link previous exit rates to future dimensions of entrepreneurial activity. Keywords: Entrepreneurship, business exits, social values, industrial organization Paper type: Research paper

Platform pricing and consumer foresight: The case of airports

Airports have become platforms that derive revenues from both aeronautical and commercial activities. The demand for these services is characterized by a one-way complementarity in that only air travelers can purchase retail goods at the airport terminals. We analyze a model of optimal airport behavior in which this one-way complementarity is subject to consumer foresight, i.e., consumers may not anticipate in full the ex post retail surplus when purchasing a flight ticket. An airport sets landing fees, and, in addition, also chooses the retail market structure by selecting the number of retail concessions to be awarded. We find that, with perfectly myopic consumers, the airport chooses to attract more passengers via low landing fees, and also sets the minimum possible number of retailers in order to increase the concessions’ revenues, from which it obtains the largest share of profits. However, even a very small amount of anticipation of the consumer surplus from retail activities changes significantly the airport’s choices: the optimal airport policy is dependent on the degree of differentiation in the retail market. When consumers instead have perfect foresight, the airport establishes a very competitive retail market, where consumers enjoy a large surplus. This attracts passengers and it is exploited by the airport by charging higher landing fees, which then constitute the largest share of its profits. Overall, the airport’s profits are maximal when consumers have perfect foresight. Keywords: two-sided markets, platform pricing, one-way demand complementarity, consumer foresight. JEL classification: L1, L2, L93.

Chromosomal polymorphism of D. subobscura: no differences between wild males and sons of wild females

When analyzing the chromosomal polymorphism of D. subobscura natural populations it is assumed that the information provided by wild males and sons of wild females is equivalent. Thus, using both in the analysis it is possible to increase the sample size. However, it is important to verify whether there are significant differences between both groups or not. The aim of this research has been to statistically compare the results of chromosomal polymorphism of both groups. We have used data from Avala Mountain (Serbia) where D. subobscura flies were collected from the 30th May to the 5th June 2011. Avala is located 18 km south of Belgrade and the trapping place is a forest with polydominant communities of Fagetum submontanum Table 1. Number and percentage of adult flies collected in Font Groga (Barcelona, Spain) on 9th October 2013. Males and sons of wild females were crossed with virgin females of the Küsnacht strain. Third instar larvae from F1 were dissected to obtain the salivary glands and the polytene chromosomes were stained and squashed in aceto-orcein solution. No significant differences were observed for any chromosome of the karyotype: A (p-value = 0.485), J (p-value = 0.230), U (p-value =0.572), E (p-value = 0.536), and O (p-value = 0.338). Thus, it seems that the two groups can be grouped together to obtain the chromosomal polymorphism of the population.

Investigating the impact of small versus large firms on economic performance of countries and industries

Following earlier work by Audretsch et al. (2002), we assume that an optimal size-class structure exists, in terms of achieving maximal economic growth rates. Such an optimal structure is likely to exist as economies need a balance between the core competences of large firms (such as exploitation of economies of scale) and those of smaller firms (such as flexibility and exploration of new ideas). Accordingly, changes in size-class structure (i.e., changes in the relative shares in economic activity accounted for by micro, small, medium-sized and large firms) may affect macro-economic growth. Using a unique data base of the EU-27 countries for the period 2002-2008 for five broad sectors of economic activity and four size-classes, we find empirical support which suggests that, on average for these countries over this period, the share of micro and large firms may have been ‘above optimum’ (particularly in lower income EU countries) whereas the share of medium-sized firms may have been ‘below optimum’ (particularly in higher income EU countries). This evidence suggests that the transition from a ‘managed’ to an ‘entrepreneurial’ economy (Audretsch and Thurik, 2001) has not been completed yet in all countries of the EU-27. Keywords: small firms, large firms, size-classes, macro-economic performance

The International Distribution of Energy Intensities: some synthetic results

The paper examines the international distribution of energy intensities as a conventional proxy indicator of energy efficiency and sustainability in the consumption of resources, by employing some descriptive tools from the analysis of inequality and polarization. The analysis specifically focuses on the following points: firstly, inequalities are evaluated synthetically based on diverse summary measures and Lorenz curves; secondly, different factorial decompositions are undertaken that assist in investigating some explanatory factors (weighting factors, multiplicative factors and decomposition by groups); and thirdly, an analysis is made of the polarization of intensities when groups of countries are defined endogenously and exogenously. The results obtained have significant implications from both academic and political perspectives.

Estimaciones de segunda generación del PIB de la Europa Latina: España, Francia, Italia, Portugal (1950-2013)

Los cambios conceptuales y metodológicos en los sistemas empleados para la construcción de la Contabilidad Nacional de todos los países, especialmente a causa de la implantación en la UE del SEC 95, así como la revisión y corrección de los datos de población más actuales obligan a introducir modificaciones muy sustanciales en las series históricas de Cuentas Nacionales por medio de la técnica de la retropolación. La realización de los nuevos cálculos, que pueden ser calificados de auténticas estimaciones de segunda generación, ofrece para España, Francia, Italia y Portugal resultados muy interesantes. Las tasas de crecimiento acumulativo anual para el conjunto del período son muy semejantes entre sí, aunque identifican a la economía española como la que más creció, tanto en la producción de bienes y servicios como en la dimensión demográfica y también en PIB por habitante.