Transport infraestructure, sunk costs and firms' export behaviour

Transport infrastructure investment reduces the cost of distance and enables firms to establish contacts over larger distances. We study the impact of transport-cost reductions on firms’ export behaviour, accounting for the role of entry costs and other firms’ characteristics. Using Spanish data we estimate dynamic probability models controlling for firms’ unobserved heterogeneity and for the simultaneity of firms’ export and location decisions. Our results provide support for a positive effect of domestic transport improvements on firms’ exporting probability for small and medium sized firms. We find a strong effect of previous export experience, suggesting high entry costs into export markets

References made and citations received by scientific articles

This paper studies massive evidence about references made and citations received after a five-year citation window by 3.7 million articles published in 1998-2002 in 22 scientific fields. We find that the distributions of references made and citations received share a number of basic features across sciences. Reference distributions are rather skewed to the right, while citation distributions are even more highly skewed: the mean is about 20 percentage points to the right of the median, and articles with a remarkable or outstanding number of citations represent about 9% of the total. Moreover, the existence of a power law representing the upper tail of citation distributions cannot be rejected in 17 fields whose articles represent 74.7% of the total. Contrary to the evidence in other contexts, the value of the scale parameter is above 3.5 in 13 of the 17 cases. Finally, power laws are typically small but capture a considerable proportion of the total citations received.

Domestic transport cost reductions and firms’ export behaviour

Transport infrastructure investment reduces the cost of distance and enables firms to establish and maintain contacts over larger distances. Spain has developed an ambitious road building programme over the last decades, which has considerably reduced transport costs to access European markets. In this paper we depart from the traditional aggregate approach in analysing the impacts of transport infrastructure investment. In particular, we examine the export decision of Spanish manufacturing firms and test how domestic transport cost reductions affect firms’ probability of becoming exporters. We estimate models that control for unobserved heterogeneity among firms, endogeneity and initial conditions problems. Our results provide some support for a positive effect of domestic transport improvements on firms’ exporting probability. However, the magnitude of this effects is small, being the strongest effect the one due to previous export experience which suggests high entry costs into export markets

References made and citations received by scientific articles.

This article studies massive evidence about references made and citations received after a 5-year citation window by 3.7 million articles published in 1998 to 2002 in 22 scientific fields. We find that the distributions of references made and citations received share a number of basic features across sciences. Reference distributions are rather skewed to the right while citation distributions are even more highly skewed:The mean is about 20 percentage points to the right of the median, and articles with a remarkable or an outstanding number of citations represent about 9% of the total. Moreover, the existence of a power law representing the upper tail of citation distributions cannot be rejected in 17 fields whose articles represent 74.7% of the total. Contrary to the evidence in other contexts, the value of the scale parameter is above 3.5 in 13 of the 17 cases. Finally, power laws are typically small, but capture a considerable proportion of the total citations received

Transport infraestructure, sunk costs and firms' export behaviour

Transport infrastructure investment reduces the cost of distance and enables firms to establish contacts over larger distances. We study the impact of transport-cost reductions on firms’ export behaviour, accounting for the role of entry costs and other firms’ characteristics. Using Spanish data we estimate dynamic probability models controlling for firms’ unobserved heterogeneity and for the simultaneity of firms’ export and location decisions. Our results provide support for a positive effect of domestic transport improvements on firms’ exporting probability for small and medium sized firms. We find a strong effect of previous export experience, suggesting high entry costs into export markets.Export decision, Transport infrastructure, Accessibility, Dynamic panel data

High- and low-impact citation measures : empirical applications.

This paper contains the first empirical applications of a novel methodology for comparing the citation distributions of research units working in the same homogeneous field. The paper considers a situation in which the world citation distribution in 22 scientific fields is partitioned into three geographical areas: the U.S., the European Union (EU), and the rest of the world (RW). Given a critical citation level (CCL), we suggest using two real valued indicators to describe the shape of each area’s distribution: a high- and a low-impact measure defined over the set of articles with citations below or above the CCL. It is found that, when the CCL is fixed at the 80th percentile of the world citation distribution, the U.S. performs dramatically better than the EU and the RW according to both indicators in all scientific fields. This superiority generally increases as we move from the incidence to the intensity and the citation inequality aspects of the phenomena in question. Surprisingly, changes observed when the CCL is increased from the 80th to the 95th percentile are of a relatively small order of magnitude. Finally, it is found that international co-authorship increases the high-impact and reduces the low-impact level in the three geographical areas. This is especially the case for the EU and the RW when they cooperate with the U.S.Research evaluation; Citation distribution; Scientific ranking; Impact indicators;

Average-based versus high-and low-impact indicators for the evaluation of scientific distributions

Albarran et al. (2011a) introduced a novel methodology for the evaluation of citation distributions consisting of a pair of high- and a low-impact measures defined over the set of articles with citations below or above a critical citation level CCL. Albarran et al. (2011b) presented the first empirical applications to a situation in which the world citation distribution in 22 scientific fields is partitioned into three geographical areas: the U.S., the European Union, and the rest of the world. In this paper, we compare our results with those obtained with average-based indicators. For reasonable CCLs, such as the 80th percentile of the world citation distribution in each field, the cardinal differences between the results obtained with our high-impact index and the mean citation rate are of a large order of magnitude. When, in addition, the percentage in the top 5% of most cited articles or the percentage of uncited articles are used, there are still important quantitative differences with respect to the high- and low-impact indicators advocated in our approach when the CCL is fixed at the 80th or the 95th percentile.

High - and low-impact citation measures: empirical applications

This paper contains the first empirical applications of a novel methodology for comparing the citation distributions of research units working in the same homogeneous field. The paper considers a situation in which the world citation distribution in 22 scientific fields is partitioned into three geographical areas: the U.S., the European Union (EU), and the rest of the world (RW). Given a critical citation level (CCL), we suggest using two real valued indicators to describe the shape of each area’s distribution: a high- and a low-impact measure defined over the set of articles with citations below or above the CCL. It is found that, when the CCL is fixed at the 80th percentile of the world citation distribution, the U.S. performs dramatically better than the EU and the RW according to both indicators in all scientific fields. This superiority generally increases as we move from the incidence to the intensity and the citation inequality aspects of the phenomena in question. Surprisingly, changes observed when the CCL is increased from the 80th to the 95th percentile are of a relatively small order of magnitude. Finally, it is found that international co-authorship increases the high-impact and reduces the low-impact level in the three geographical areas. This is especially the case for the EU and the RW when they cooperate with the U.S.

The measurement of low- and high-impact in citation distributions : technical results.

This paper introduces a novel methodology for comparing the citation distributions of research units of a certain size working in the same homogeneous field. Given a critical citation level (CCL), we suggest using two real valued indicators to describe the shape of any distribution: a high-impact and a low-impact measure defined over the set of articles with citations above or below the CCL. The key to this methodology is the identification of a citation distribution with an income distribution. Once this step is taken, it is easy to realize that the measurement of low-impact coincides with the measurement of economic poverty. In turn, it is equally natural to identify the measurement of high-impact with the measurement of a certain notion of economic affluence. On the other hand, it is seen that the ranking of citation distributions according to a family of low-impact measures is essentially characterized by a number of desirable axioms. Appropriately redefined, these same axioms lead to the selection of an equally convenient class of decomposable high-impact measures. These two families are shown to satisfy other interesting properties that make them potentially useful in empirical applications, including the comparison of research units working in different fieldsResearch performance; Citation distribution; Poverty measurement; Impact indicators;

Inequality for Wage Earners and Self-Employed: Evidence from Panel Data

Published as an article in: Oxford Bulletin of Economics and Statistics, 2009, vol. 71, issue 4, pages 491-518.transitory income inequality, consumption, permanent income inequality, self-employment, panel data