Issues in the analysis of co-authorship networks

Scientific collaboration is a complex phenomenon that improves the sharing of competences and the production of new scientific knowledge. Social Network Analysis is often used to describe the scientific collaboration patterns defined by co-authorship relationships. Different phases of the analysis of collaboration are related to: data collection, network boundary setting, relational data matrix definition, data analysis and interpretation of results. The aim of this paper is to point out some issues that arise in these different phases, highlighting: (i) the use of local archives versus international bibliographic databases; (ii) the use of different approaches for setting boundaries in a whole-network; (iii) the definition of a co-authorship data matrix (binary and weighted ties) and (iv) the analysis and the interpretation of network measures for co-authorship data. We discuss the different choices that can be made in these phases within an illustrative example on real data which is referred to scientific collaboration among researchers affiliated to an academic institution. In particular, we compare global and actor-level network measures computed from binary and weighted co-authorship networks in different disciplines.     

MIND THE GAP: UNEMPLOYMENT IN THE NEW EU REGIONS

Abstract.  The paper surveys the theoretical and empirical literature on regional unemployment during transition in Central and Eastern Europe. The focus is on optimal speed of transition (OST) models and on comparison of them with the neo-classical tradition. In the typical neo-classical models, spatial differences essentially arise as a consequence of supply side constraints and institutional rigidities. Slow-growth, high-unemployment regions are those with backward economic structures and constraints on factors mobility contribute to making differences persistent. However, such explanations leave the question unanswered of how unemployment differences arise in the first place. Economic transition provides an excellent testing ground to answer this question. Pre-figuring an empirical law, the OST literature finds that the high degree of labour turnover of high unemployment regions is associated with a high rate of industrial restructuring and, consequently, that low unemployment may be achieved by implementing transition more gradually. Moreover, international trade, foreign direct investment and various agglomeration factors help explain the success of capital cities compared to peripheral towns and rural areas in achieving low unemployment. The evidence of the empirical literature on supply side factors suggests that wage flexibility in Central and Eastern Europe is not lower than in other EU countries, while labour mobility seems to reinforce rather than change the spatial pattern of unemployment.     

Model misspecification effects for biased samples

The model misspecification effects on the maximum likelihood estimator are studied when a biased sample is treated as a random one as well as when a random sample is treated as a biased one. The relation between the existence of a consistent estimator under model misspecification and the completeness of the distribution is also considered. The cases of the weight invariant distribution and the scale parameter distribution are examined and finally an example is presented to illustrate the results.     

Raising the bar (6)

Raising the bar (6). Spatial Economic Analysis. This editorial summarizes and comments on the papers published in issue 12(4) so as to raise the bar in applied spatial economic research and highlight new trends. The first paper addresses the question of whether ‘jobs follow people’ or ‘people follow jobs’. The second paper develops a new methodology to determine functional regions. The third paper is a major contribution to the growing literature on new modelling approaches and applications of disaster impact models. The fourth paper focuses on the costs and benefits of higher education. The fifth paper develops a two-step procedure to identify endogenously spatial regimes in the first step using geographically weighted regression, and to account for spatial dependence in the second step. Finally, the sixth paper estimates a dynamic spatial panel data model to explain house prices and to show that restricted housing supply in the city of Cambridge, UK, has some undesirable labour market effects.     

THE GINI CONCENTRATION INDEX: A REVIEW OF THE INFERENCE LITERATURE

More than a century ago, Corrado Gini proposed his well-known concentration index for measuring the degree of inequality in the distribution of income and wealth. His index is still extremely relevant and widely used in several fields of research and application. In this paper, we focus on the inferential properties of the Gini index, and discuss the main directions of analysis proposed in the literature. The aim of the paper is to provide a comprehensive review of the main developments on the inferential aspects of the Gini concentration ratio. We feel that this work can provide a valuable contribution to those scholars who are approaching the large amount of literature on the inferential properties of the Gini index.     

Congestion games with load-dependent failures: Identical resources

We define a new class of games, congestion games with load-dependent failures (CGLFs). In a CGLF each player can choose a subset of a set of available resources in order to try and perform his task. We assume that the resources are identical but that players' benefits from successful completion of their tasks may differ. Each resource is associated with a cost of use and a failure probability which are load-dependent. Although CGLFs in general do not have a pure strategy Nash equilibrium, we prove the existence of a pure strategy Nash equilibrium in every CGLF with nondecreasing cost functions. Moreover, we present a polynomial time algorithm for computing such an equilibrium.     

Fundamentals, the exchange rate and prospects for the current and future EU enlargements: evidence from Bulgaria, Croatia, Romania and Turkey

We analyze the link between macroeconomic fundamentals and exchange rate dynamics in two new and two potential EU member states: Bulgaria, Romania, Croatia, and Turkey. Given the different institutional settings of the exchange rate market in the countries of interest, we follow two different modelling strategies. For Romania and Turkey, we evaluate possible exchange rate misalignments based on a monetary model of exchange rate determination. In the case of Bulgaria and Croatia, with currency board and narrow-band peg arrangements against the euro, we discuss possible exit strategies and quantitatively assess the effects of the peg arrangements by means of simulation.

Abnormal returns before acquisition announcements: evidence from Europe

Acquisition announcements influence the stock price of target firms, providing an opportunity for insiders to obtain significant abnormal returns. We study the presence of positive abnormal returns before the announcement date, in target firms, quoted in Euronext markets (Belgium, France, The Netherlands and Portugal) from 2001 to 2007. We investigate whether the pre-announcement run-up of prices can be explained by rumours in the media and the percentage of capital previously owned by the bidding firm, among other factors. We examine cumulative abnormal returns in an event window of 60 days prior the acquisition announcement, with the event date adjusted for the previous disclosure of news about the acquisition, in the media. We compute a run-up index, and find that there are abnormal positive returns before the announcement date, confirming previous studies. We find that a significant part of the run-up is explained by: (i) market anticipation triggered by legitimate sources of information, namely, rumours in the media about the possibility of an acquisition bid and (ii) the percentage of capital previously owned in the target firm, by the bidding firm.     

Geographical concentration and the dynamics of countries' specialization in technologies

This paper examines the empirical dynamics of countries' technological specialization in six technology fields using distribution dynamics. In all technology fields innovation activities are performed by relatively few countries and the degree of concentration is fairly stable in time. Intra-distribution dynamics is characterized by persistence of within field countries' specialization levels around or below the mean, while high specialization levels revert towards lower values. This strengthens the case for absorptive capacity. Electronics show some distinctive properties: they have the highest degree of geographical concentration and numerous small countries among those specialized; they also are the least mobile technology field. In a Schumpeterian perspective, this is in line with "creative accumulation".