Introducing a general class of species diversification models for phylogenetic trees

Phylogenetic trees are types of networks that describe the temporal relationship between individuals, species, or other units that are subject to evolutionary diversification. Many phylogenetic trees are constructed from molecular data that is often only available for extant species, and hence they lack all or some of the branches that did not make it into the present. This feature makes inference on the diversification process challenging. For relatively simple diversification models, analytical or numerical methods to compute the likelihood exist, but these do not work for more realistic models in which the likelihood depends on properties of the missing lineages. In this article, we study a general class of species diversification models, and we provide an expectation-maximization framework in combination with a uniform sampling scheme to perform maximum likelihood estimation of the parameters of the diversification process.     

Cyclicality in losses on bank loans

Based on unique data we show that macro variables, the default rate and loss given default of bank loans share common cyclical components. The innovation in our model is the distinction between loans with either severe or mild losses. The variation in the proportion of these two types drives the cyclic behavior of the loss given default and constitutes the links with the default rate and macro variables. These links vary according to loan and borrower characteristics. During downturns, the proportion of defaults with severe losses increases, but the distribution of losses conditional on their being mild or severe does not change. although loans are monitored more closely than bonds and are more senior, the cyclical variation in their losses resembles those for bonds, albeit around a lower average level. This variation leads to an increase in the capital reserves required for loan portfolios.     

Information technology,transaction costs and the decision to 'make or buy'

Information and communication technology (ICT) has a wide ranging impact on business. One of the effects is on the 'make or buy decision'. This is analysed from the perspective of transactzon cost economm (TCE). On the one hand ICT reduces transaction costs by reducing search costs, by facilitating monitoring and control of performance and by yielding a greater flexibility of production, which reduces the transaction specificity of assets. These efiects, favour the decision to 'buy'. On the other hand, ICT reduces economies of scale, in some areas of production, which makes outside production i n a specializedfirm less attractive. Also, ICT may be used to impose switching costs between suppliers and buyers, thereby miszng transaction costs. But such ploys appear to be feasible only temporarily, with a pressure from users and competitors towards standardization and open systems. Thus the effects of ICT are diverse, but on the whole it tends to favour the option to contract out.     

Use Tables for Imported Goods and Valuation Matrices for Trade Margins—an Integrated Approach for the Compilation of the Belgian 1995 Input–Output Tables

This paper describes the compilation of the use table for imported goods and the valuation matrix of trade margins for Belgium in 1995. It introduces the methodological novelty of integrating the compilation of both tables and systematically exploiting the fact that large import and export flows do not generate trade margins. This is notably the case for direct imports for intermediate consumption or investment by non-traders, and direct exports by producers. For identifying these trade flows, extensive use was made of intrastat and extrastat data. The results are compared with those of a proportional distribution of imports and trade margins. Many statistical offices resort to the latter approach because of a lack of survey data on the destination of trade margins and imports. We demonstrate that the integrated approach can improve the quality of both the import matrix and the valuation matrix for trade margins, while using only existing data sources.     

An Illustrated User Guide to the World Input–Output Database: the Case of Global Automotive Production

This article provides guidance to prudent use of the World Input–Output Database (WIOD) in analyses of international trade. The WIOD contains annual time‐series of world input–output tables and factor requirements covering the period from 1995 to 2011. Underlying concepts, construction methods and data sources are introduced, pointing out particular strengths and weaknesses. We illustrate its usefulness by analyzing the geographical and factorial distribution of value added in global automotive production and show increasing fragmentation, both within and across regions. Possible improvements and extensions to the data are discussed.     

«Flexiseguridad» en Bélgica. Una propuesta de reforma basada en principios económicos

El régimen de seguro de desempleo y la legislación protectora del empleo de Bélgica se establecieron con el telón de fondo de una relación clásica, de carácter estable y duradero, entre trabajadores y empresas. Sin embargo, la globalización de la economía y la rápida evolución de las tecnologías y los sistemas de organización exigen hoy en día más flexibilidad tanto a unos como a otras. De ahí que las instituciones del mercado laboral hayan de reformarse de manera urgente para conciliar esta mayor flexibilidad con una seguridad suficiente para los trabajadores. Aunque la idea de la «flexiseguridad» no es nueva, hay opiniones distintas sobre cuál es el modelo institucional que debe traer consigo. Los autores proponen una reforma guiada expresamente por los principios económicos.     

Road transport productivity in the sixteenth‐century Low Countries: the case of Brabant, 1450–1650†

Though there is a consensus that transport plays a central role in economic development, for the period before the eighteenth century there is a lack of strategic information for assessing the importance of road transport productivity changes in economic development. Transport prices in particular are crucial missing pieces of the puzzle. Sources rarely reveal information that meets the standards of reliable price history. However, it is possible to create a reliable transport price series on the basis of the transport of millstones to ducal mills in Brabant. Assessing the impact of the ‘transport productivity changes’ that can be inferred from this transport price series is a hazardous exercise. Moreover, as Masschaele has observed, land transport prices closely match general agricultural price trends. Land transport was essentially an agricultural service, determined both by cost (especially horse provender) and income effects. Transport price inflation was not demand‐led. However, while transport did not impede urbanization and economic growth, conversely, in sixteenth‐century Brabant—a highly urbanized region that experienced considerable growth in the volume of land transport—no significant land transport productivity gains were achieved.     

Does access to improved grain storage technology increase farmers' welfare? Experimental evidence from maize farming in Ethiopia

Seasonal price variability for cereals is two to three times higher in Africa than on the international reference market. Seasonality is even more pronounced when access to appropriate storage and opportunities for price arbitrage are limited. As smallholder farmers typically sell their production after harvest, when prices are low, this leads to lower incomes as well as higher food insecurity during the lean season, when prices are high. One solution to reduce seasonal stress is the use of improved storage technologies. Using data from a randomised controlled trial, in a major maize-growing region of Western Ethiopia, we study the impact of hermetic bags, a technology that protects stored grain against insect pests, so that the grain can be stored longer. Despite considerable price seasonality—maize prices in the lean season are 36% higher than after harvesting—we find no evidence that hermetic bags improve welfare, except that access to these bags allowed for a marginally longer storage period of maize intended for sale by 2 weeks. But this did not translate into measurable welfare gains as we found no changes in any of our welfare outcome indicators. This ‘near-null’ effect is due to the fact that maize storage losses in our study region are relatively lower than previous studies suggested—around 10% of the quantity stored—likely because of the widespread use of an alternative to protect maize during storage, for example a cheap but highly toxic fumigant. These findings are important for policies that seek to promote improved storage technologies in these settings.