Marginal effects in the double selection regression model: an illustration for the wages of women in Spain

In this article we obtain different marginal effects for continuous variables in the context of a double selection regression model, in which it is assumed that the model's disturbances have a normal distribution. Using data of Spanish women, we illustrate these effects by estimating a double selection regression model for the analysis of the economic return from education in the context of the Mincerian wage equation.wage equation

AN AGGREGATED INDEX OF HUMAN CAPITAL

In this paper, taking the model of Arrazola and Hevia (Applied Economics Letters, 11 – 145-8, 2004) as a starting point, we propose a homogeneous measure of human capital of individuals, which permits interpersonal comparisons. This indicator has been set up for a sample of Spanish men and women and compared to the results obtained when using Portela's proposal to construct a human capital indicator (Economics Letters, 72, 27-32, 2001). It was concluded that both from a theoretical and empirical point of view, the properties of the index proposed in this article are better than those of Portela''s suggested measure.human capital.

An optimization model for metabolic pathways

This article is available open access through the publisher’s website through the link below. Copyright @ The Author 2009.Motivation: Different mathematical methods have emerged in the post-genomic era to determine metabolic pathways. These methods can be divided into stoichiometric methods and path finding methods. In this paper we detail a novel optimization model, based upon integer linear programming, to determine metabolic pathways. Our model links reaction stoichiometry with path finding in a single approach. We test the ability of our model to determine 40 annotated Escherichia coli metabolic pathways. We show that our model is able to determine 36 of these 40 pathways in a computationally effective manner. Contact: [email protected] Supplementary information: Supplementary data are available at Bioinformatics online (http://bioinformatics.oxfordjournals.org/cgi/content/full/btp441/DC1)

A simple inflation indicator for the euro zone

This paper proposes and estimates an inflation indicator for the European Monetary Union (EMU). This indicator is set up so that it is contemporarily not affected by the changes in price differentials among EMU countries. The results show that the Monetary Union Index of Consumer Prices (MUICP), which is the inflation measure that the European Central Bank (ECB) takes as a reference for monetary policy purposes, could be understating the value of the inflation in the euro zone. It is also concluded that regional peculiarities are fundamental in the evolution of prices in the different EMU countries

A proposal to estimate human capital depreciation: some evidence for Spain

This article formulates an empirical model for salary determination, which permits the identification of the depreciation rate of the stock of professional qualifications. The analysis is implemented using the 1994 European Community Household Panel data referring to Spanish salaried males. The depreciation rate of the stock of qualifications is estimated at a narrow interval centred at 1%. Empirical evidence also suggests that although the depreciation rate does not vary according to the level of education, it does so depending on unemployment spells endured by the worker in recent years and on whether the worker has undertaken training courses.Human capital, depreciation, experience-earnings profiles

Not All Continuous Dimensions Map Equally: Number-Brightness Mapping in Human Infants

Evidence for spontaneous mappings between the dimensions of number and length, time and length, and number and time, has been recently described in preverbal infants. It is unclear, however, whether these abilities reflect the existence of privileged mappings between certain quantitative dimensions, like number, space and time, or instead the existence of a magnitude system underlying the representation of any quantitative dimension, and allowing mappings across those dimensions. Four experiments, using the same methods from previous research that revealed a number-length mapping in eight-month-old infants, investigated whether infants of the same age establish mappings between number and a different, non-spatial continuous dimension: level of brightness. We show that infants are able to learn and productively use mappings between brightness and number when they are positively related, i.e., larger numbers paired with brighter or higher contrast levels, and fail when they are inversely related, i.e., smaller numbers paired with brighter or higher contrast levels, suggesting that they are able to learn this mapping in a specific direction. However, infants not only do not show any baseline preference for any direction of the number-brightness mapping, but fail at transferring the discrimination from one dimension (number) to the other (brightness). Although infants can map multiple dimensions to one another, the number-length mapping may be privileged early in development, as it is for adults

Number-Space Mapping in Human Infants

Mature representations of number are built on a core system of numerical representation that connects to spatial representations in the form of a mental number line. The core number system is functional in early infancy, but little is known about the origins of the mapping of numbers onto space. In this article, we show that preverbal infants transfer the discrimination of an ordered series of numerosities to the discrimination of an ordered series of line lengths. Moreover, infants construct relationships between numbers and line lengths when they are habituated to unordered pairings that vary positively, but not when they are habituated to unordered pairings that vary inversely. These findings provide evidence that a predisposition to relate representations of numerical magnitude to spatial length develops early in life. A central foundation of mathematics, science, and technology therefore emerges prior to experience with language, symbol systems, or measurement devices.Psycholog