Analysing and controlling the tax evasion dynamics via majority-vote model

Within the context of agent-based Monte-Carlo simulations, we study the well-known majority-vote model (MVM) with noise applied to tax evasion on simple square lattices, Voronoi-Delaunay random lattices, Barabasi-Albert networks, and Erd\"os-R\'enyi random graphs. In the order to analyse and to control the fluctuations for tax evasion in the economics model proposed by Zaklan, MVM is applied in the neighborhod of the noise critical $q_{c}$. The Zaklan model had been studied recently using the equilibrium Ising model. Here we show that the Zaklan model is robust and can be reproduced also through the nonequilibrium MVM on various topologies.Comment: 18 pages, 7 figures, LAWNP'09, 200

Opinion dynamics: models, extensions and external effects

Recently, social phenomena have received a lot of attention not only from social scientists, but also from physicists, mathematicians and computer scientists, in the emerging interdisciplinary field of complex system science. Opinion dynamics is one of the processes studied, since opinions are the drivers of human behaviour, and play a crucial role in many global challenges that our complex world and societies are facing: global financial crises, global pandemics, growth of cities, urbanisation and migration patterns, and last but not least important, climate change and environmental sustainability and protection. Opinion formation is a complex process affected by the interplay of different elements, including the individual predisposition, the influence of positive and negative peer interaction (social networks playing a crucial role in this respect), the information each individual is exposed to, and many others. Several models inspired from those in use in physics have been developed to encompass many of these elements, and to allow for the identification of the mechanisms involved in the opinion formation process and the understanding of their role, with the practical aim of simulating opinion formation and spreading under various conditions. These modelling schemes range from binary simple models such as the voter model, to multi-dimensional continuous approaches. Here, we provide a review of recent methods, focusing on models employing both peer interaction and external information, and emphasising the role that less studied mechanisms, such as disagreement, has in driving the opinion dynamics. [...]Comment: 42 pages, 6 figure

A Biased Review of Sociophysics

Various aspects of recent sociophysics research are shortly reviewed: Schelling model as an example for lack of interdisciplinary cooperation, opinion dynamics, combat, and citation statistics as an example for strong interdisciplinarity.Comment: 16 pages for J. Stat. Phys. including 2 figures and numerous reference

Offset Credits in the EU ETS: A Quantile Estimation of Firm-Level Transaction Costs

International offset certificates trade at lower prices than European Union Allowances (EUAs), although they are substitutes within the EU Emissions Trading System (EU ETS) for CO2. Firms therefore had a strong incentive to use the cheaper certificates. However, a considerable number of firms did not use their allowed offset quota and, by doing so, seemingly forwent profits. While most of the literature on emissions trading evaluates the efficiency of regulation in a frictionless world, in practice firms incur costs when complying with regulation. In order to assess the relevance of managerial and information-related transaction costs, this study examines the use of international offset credits in the EU ETS. It establishes a model of firm decision under fixed entry costs and estimates the size of transaction costs rationalizing firm behavior using semi-parametric binary quantile regressions. Comparing binary quantile results with probit estimates shows that high average transaction cost result from a strongly skewed underlying distribution. I find that for most firms the bulk of transaction costs stems from participation in the EU ETS in general, rather than additional participation in the offset trade

The Globalization of Steam Coal Markets and the Role of Logistics: An Empirical Analysis

In this paper, we provide a comprehensive multivariate cointegration analysis of three parts of the steam coal value chain - export, transport and import prices. The analysis is based on a rich dataset of international coal prices; in particular, we combine data on steam coal prices with freight rates, covering the period December 2001 until August 2009 at weekly frequency. We then test whether the demand and supply side components of steam coal trade are consistently integrated with one another. In addition, export and import prices as well as freight rates for individual trading routes, across regions and globally are combined. We find evidence of significant yet incomplete integration. We also find heterogeneous short-term dynamics of individual markets. Furthermore, we examine whether logistics enter coal price dynamics through transportation costs, which are mainly determined by oil prices. Our results suggest that this is generally not the case

The Dynamics of Global Crude Oil Production

We analyze the dynamic effect of prices and price volatility on current oil production, both on the level of country groups and the major individual producer countries. A comprehensive dataset at monthly frequency allows us to include a rich lag structure while controlling for key global and local determinants as well as seasonality. Our set of explanatory variables also includes real economic activity, investment, the strength of the U.S. dollar and institutional quality. We provide a naïve regression analysis using a broad model to show that lagged explanatory variables are important determinants of current oil production. We find that the reaction of oil production is heterogeneous across both country groups and the major individual producer countries

Systematic and Evolutionary Insights Derived from mtDNA COI Barcode Diversity in the Decapoda (Crustacea: Malacostraca)

Background: Decapods are the most recognizable of all crustaceans and comprise a dominant group of benthic invertebrates of the continental shelf and slope, including many species of economic importance. Of the 17635 morphologically described Decapoda species, only 5.4% are represented by COI barcode region sequences. It therefore remains a challenge to compile regional databases that identify and analyse the extent and patterns of decapod diversity throughout the world. Methodology/Principal Findings: We contributed 101 decapod species from the North East Atlantic, the Gulf of Cadiz and the Mediterranean Sea, of which 81 species represent novel COI records. Within the newly-generated dataset, 3.6% of the species barcodes conflicted with the assigned morphological taxonomic identification, highlighting both the apparent taxonomic ambiguity among certain groups, and the need for an accelerated and independent taxonomic approach. Using the combined COI barcode projects from the Barcode of Life Database, we provide the most comprehensive COI data set so far examined for the Order (1572 sequences of 528 species, 213 genera, and 67 families). Patterns within families show a general predicted molecular hierarchy, but the scale of divergence at each taxonomic level appears to vary extensively between families. The range values of mean K2P distance observed were: within species 0.285% to 1.375%, within genus 6.376% to 20.924% and within family 11.392% to 25.617%. Nucleotide composition varied greatly across decapods, ranging from 30.8 % to 49.4 % GC content. Conclusions/Significance: Decapod biological diversity was quantified by identifying putative cryptic species allowing a rapid assessment of taxon diversity in groups that have until now received limited morphological and systematic examination. We highlight taxonomic groups or species with unusual nucleotide composition or evolutionary rates. Such data are relevant to strategies for conservation of existing decapod biodiversity, as well as elucidating the mechanisms and constraints shaping the patterns observed.FCT - SFRH/BD/25568/ 2006EC FP6 - GOCE-CT-2005-511234 HERMESFCT - PTDC/MAR/69892/2006 LusomarBo

COALMOD-World: A Model to Assess International Coal Markets Until 2030

Coal continues to be an important fuel in many countries' energy mix and, despite the climate change concerns, it is likely to maintain this position for the next decades. In this paper a numerical model is developed to investigate the evolution of the international market for steam coal, the coal type used for electricity generation. The main focus is on future trade ows and investments in production and transport infrastructure until 2030. COALMOD-World is an equilibrium model, formulated in the complementarity format. It includes all major steam coal exporting and importing countries and represents the international trade as one globalized market. Some suppliers of coal are at the same time major consumers, such as the USA and China. Therefore, domestic markets are also included in the model to analyze their interaction with the international market. Because of the different qualities of steam coal, we include different heating values depending on the origin of the coal. At the same time we observe the mass-specific constraints on production, transport and export capacity. The time horizon of our analysis is until 2030, in 5-year steps. Production costs change endogenously over time. Moreover, endogenous investments are included based on a net present value optimization approach and and the shadow prices of capacities constraints. Investments can be carried out in production, inland freight capacities (rail in most countries), and export terminals. The paper finishes with an application of the model to a base case scenario and suggestions for alternative scenarios

Left-right asymmetry of fly wings and the evolution of body axes.

The body plan of Drosophila, and presumably that of other insects, develops under the control of anterio-posterior and dorsal ventral axes, but no evidence for a left-right axis has yet been found. We used geometric morphometrics to study the wings in three species of flies: Drosophila melanogaster, Musca domestica and Glossina palpalis gambiensis. In all three species, we found that both size and shape showed subtle, but statistically significant directional asymmetry. For size, these asymmetries were somewhat inconsistent within and between species, but for shape, highly significant directional asymmetry was found in all samples examined. These systematic left-right differences imply the existence of a left-right axis that conveys distinct positional identities to the wing imaginal discs on either body side. Hence, the wing discs of Drosophila may be a new model to study the developmental genetics of left-right asymmetry. The asymmetries of shape were similar among species, suggesting that directional asymmetry has been evolutionarily conserved since the three lineages diverged. We discuss the implications of this evolutionary conservatism in conjunction with results from earlier studies that showed a lack of genetic variation for directional asymmetry in Drosophila