4,569 research outputs found
Comparison of Frontier Efficiency Methods: An Application to the U.S. Life Insurance Industry
The objective of this paper is to provide new information on the performance of efficiency estimation methods by applying a wide range of econometric and mathematical programming techniques to a sample of U.S. life insurers. Average efficiencies differ significantly across methods. The efficiency rankings are well-preserved among the econometric methods; but the rankings are less consistent between the econometric and mathematical programming methods and between the data envelopment analysis and free disposal hull techniques. Thus, the choice of estimation method can have a significant effect on the conclusions of an efficiency study. Most of the insurers in the sample display either increasing or decreasing returns to scale, and stock and mutual insurers are found to be equally efficient after controlling for firm size. Key words: Efficiency estimation, stochastic frontiers, data envelopment analysis, free disposal hull, life insurance industry, organizational form.
Organizational Form and Efficiency: An Analysis of Stock and Mutual Property-Liability Insurers
This paper analyzes the efficiency of stock and mutual organizational forms in the property-liability insurance industry using nonparametric frontier efficiency methods. We test the managerial discretion hypothesis, which predicts that the market will sort organizational forms into market segments where they have comparative advantages in minimizing the costs of production, including agency costs. Both production and cost frontiers are estimated. The results indicate that stocks and mutuals are operating on separate production and cost frontiers and thus represent distinct technologies. The stock technology dominates the mutual technology for producing stock output vectors and the mutual technology dominates the stock technology for producing mutual output vectors. However, the stock cost frontier dominates the mutual cost frontier for the majority of both stock and mutual firms. Thus, the mutuals' technological advantage is eroded because they are less successful than stocks in choosing cost-minimizing combinations of inputs. The finding of separate frontiers and organization specific technological advantages is consistent with the managerial discretion hypothesis, but we also find evidence that stocks are more successful than mutuals in minimizing costs.
Band structure renormalization and weak pseudogap behavior in Na_{0.33}CoO_2: Fluctuation exchange study based on a single band model
Based on a single band Hubbard model and the fluctuation exchange
approximation, the effective mass and the energy band renormalization in
NaCoO is elaborated. The renormalization is observed to exhibit
certain kind of anisotropy, which agrees qualitatively with the angle-resolved
photoemission spectroscopy (ARPES) measurements. Moreover, the spectral
function and density of states (DOS) in the normal state are calculated, with a
weak pseudogap behavior being seen, which is explained as a result of the
strong Coulomb correlations. Our results suggest that the large Fermi surface
(FS) associated with the band plays likely a central role in the
charge dynamics.Comment: 5 pages, 5 figure
Conglomeration Versus Strategic Focus: Evidence from the Insurance Industry
We provide evidence on the validity of the conglomeration hypothesis versus the strategic focus hypothesis for financial institutions using data on U.S. insurance companies. We distinguish between the hypotheses using profit scope economies, which measures the relative efficiency of joint versus specialized production, taking both costs and revenues into account. The results suggest that the conglomeration hypothesis dominates for some types of financial service providers and the strategic focus hypothesis dominates for other types. This may explain the empirical puzzle of why joint producers and specialists both appear to be competitively viable in the long run.
Quantified Uncertainty in Thermodynamic Modeling for Materials Design
Phase fractions, compositions and energies of the stable phases as a function
of macroscopic composition, temperature, and pressure (X-T-P) are the principle
correlations needed for the design of new materials and improvement of existing
materials. They are the outcomes of thermodynamic modeling based on the
CALculation of PHAse Diagrams (CALPHAD) approach. The accuracy of CALPHAD
predictions vary widely in X-T-P space due to experimental error, model
inadequacy and unequal data coverage. In response, researchers have developed
frameworks to quantify the uncertainty of thermodynamic property model
parameters and propagate it to phase diagram predictions. In previous studies,
uncertainty was represented as intervals on phase boundaries (with respect to
composition) or invariant reactions (with respect to temperature) and was
unable to represent the uncertainty in eutectoid reactions or in the stability
of phase regions. In this work, we propose a suite of tools that leverages
samples from the multivariate model parameter distribution to represent
uncertainty in forms that surpass previous limitations and are well suited to
materials design. These representations include the distribution of phase
diagrams and their features, as well as the dependence of phase stability and
the distributions of phase fraction, composition activity and Gibbs energy on
X-T-P location - irrespective of the total number of components. Most
critically, the new methodology allows the material designer to interrogate a
certain composition and temperature domain and get in return the probability of
different phases to be stable, which can positively impact materials design
Computational study of structural and elastic properties of random AlGaInN alloys
In this work we present a detailed computational study of structural and
elastic properties of cubic AlGaInN alloys in the framework of Keating valence
force field model, for which we perform accurate parametrization based on state
of the art DFT calculations. When analyzing structural properties, we focus on
concentration dependence of lattice constant, as well as on the distribution of
the nearest and the next nearest neighbour distances. Where possible, we
compare our results with experiment and calculations performed within other
computational schemes. We also present a detailed study of elastic constants
for AlGaInN alloy over the whole concentration range. Moreover, we include
there accurate quadratic parametrization for the dependence of the alloy
elastic constants on the composition. Finally, we examine the sensitivity of
obtained results to computational procedures commonly employed in the Keating
model for studies of alloys
Enhanced transmission of optically thick metallic films at infrared wavelengths
For an optically thick metallic film, the transmission for both s- and
p-polarized waves is extremely low. If the metallic film is coated on both
sides with a finite dielectric layer, light transmission for -polarized
waves can be enhanced considerably. This enhancement is not related to surface
plasmon-polaritions. Instead, it is due to the interplay between Fabry-Perot
interference in the coated dielectric layer and the existence of the Brewster
angle at the dielectric/metallic interface. It is shown that the coated
metallic films can act as excellent polarizers at infrared wavelengths.Comment: 3 pages, 4 figures. Submitted to Appl. Phys. Let
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