15,982 research outputs found
About the Accuracy of Gini Index for Measuring the Poverty
The Gini index is often used to measure the income inequality presented inside a specified group of individuals and sometimes also for evaluating the “poverty” degree of this population. In this article we show that Gini’s index is not always so adequate to measure the poverty level of an analyzed population. More precisely, we’ll get two very different income distributions which finally give the same value for Gini’s index. Having in mind this aspect, we recommend with priority to use the Gini index only together with other similar or complementary poverty indicators to evaluate the poverty level of a given population.measurement and analysis of poverty, Gini index, Lorenz curve, income distribution, inequality index
Molecular dynamics study of the stability of a carbon nanotube atop a catalytic nanoparticle
The stability of a single-walled carbon nanotube placed on top of a catalytic
nickel nanoparticle is investigated by means of molecular dynamics simulations.
As a case study, we consider the nanotube consisting of 720 carbon
atoms and the icosahedral Ni cluster. An explicit set of
constant-temperature simulations is performed in order to cover a broad
temperature range from 400 to 1200 K, at which a successful growth of carbon
nanotubes has been achieved experimentally by means of chemical vapor
deposition. The stability of the system depending on parameters of the involved
interatomic interactions is analyzed. It is demonstrated that different
scenarios of the nanotube dynamics atop the nanoparticle are possible depending
on the parameters of the Ni-C potential. When the interaction is weak the
nanotube is stable and resembles its highly symmetric structure, while an
increase of the interaction energy leads to the abrupt collapse of the nanotube
in the initial stage of simulation. In order to validate the parameters of the
Ni-C interaction utilized in the simulations, DFT calculations of the potential
energy surface for carbon-nickel compounds are performed. The calculated
dissociation energy of the Ni-C bond is in good agreement with the values,
which correspond to the case of a stable and not deformed nanotube simulated
within the MD approach.Comment: 11 pages, 5 figures; submitted to Eur. Phys. J.
Incentivizing Resilience in Financial Networks
When banks extend loans to each other, they generate a negative externality
in the form of systemic risk. They create a network of interbank exposures by
which they expose other banks to potential insolvency cascades. In this paper,
we show how a regulator can use information about the financial network to
devise a transaction-specific tax based on a network centrality measure that
captures systemic importance. Since different transactions have different
impact on creating systemic risk, they are taxed differently. We call this tax
a Systemic Risk Tax (SRT). We use an equilibrium concept inspired by the
matching markets literature to show analytically that this SRT induces a unique
equilibrium matching of lenders and borrowers that is systemic-risk efficient,
i.e. it minimizes systemic risk given a certain transaction volume. On the
other hand, we show that without this SRT multiple equilibrium matchings exist,
which are generally inefficient. This allows the regulator to effectively
stimulate a `rewiring' of the equilibrium interbank network so as to make it
more resilient to insolvency cascades, without sacrificing transaction volume.
Moreover, we show that a standard financial transaction tax (e.g. a Tobin-like
tax) has no impact on reshaping the equilibrium financial network because it
taxes all transactions indiscriminately. A Tobin-like tax is indeed shown to
have a limited effect on reducing systemic risk while it decreases transaction
volume.Comment: 38 pages, 9 figure
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