14,613 research outputs found
The quality of parallel imports
This paper empirically analyzes the change in the quality of parallel import goods (goods that are traded without the permission of the intellectual property right holder) across countries over time. Index number methodology for assessing the changes in quality of traded goods is applied to goods subject to parallel import competition in the European Union during 1995-2004. The claim that parallel import competition leads to a reduction in quality over time is not substantiated after analyzing the changes in the quality of imports to Sweden and Finland (who joined the EU in 1995 and subsequently opened their markets to parallel trade) and comparing them to changes in quality in the rest of the EU.parallel imports
Euler Characteristics of Categories and Homotopy Colimits
In a previous article, we introduced notions of finiteness obstruction, Euler
characteristic, and L^2-Euler characteristic for wide classes of categories. In
this sequel, we prove the compatibility of those notions with homotopy colimits
of I-indexed categories where I is any small category admitting a finite
I-CW-model for its I-classifying space. Special cases of our Homotopy Colimit
Formula include formulas for products, homotopy pushouts, homotopy orbits, and
transport groupoids. We also apply our formulas to Haefliger complexes of
groups, which extend Bass--Serre graphs of groups to higher dimensions. In
particular, we obtain necessary conditions for developability of a finite
complex of groups from an action of a finite group on a finite category without
loops.Comment: 44 pages. This final version will appear in Documenta Mathematica.
Remark 8.23 has been improved, discussion of Grothendieck construction has
been slightly expanded at the beginning of Section 3, and a few other minor
improvements have been incoporate
Finiteness obstructions and Euler characteristics of categories
We introduce notions of finiteness obstruction, Euler characteristic,
L^2-Euler characteristic, and M\"obius inversion for wide classes of
categories. The finiteness obstruction of a category Gamma of type (FP) is a
class in the projective class group K_0(RGamma); the functorial Euler
characteristic and functorial L^2-Euler characteristic are respectively its
RGamma-rank and L^2-rank. We also extend the second author's K-theoretic
M\"obius inversion from finite categories to quasi-finite categories. Our main
example is the proper orbit category, for which these invariants are
established notions in the geometry and topology of classifying spaces for
proper group actions. Baez-Dolan's groupoid cardinality and Leinster's Euler
characteristic are special cases of the L^2-Euler characteristic. Some of
Leinster's results on M\"obius-Rota inversion are special cases of the
K-theoretic M\"obius inversion.Comment: Final version, accepted for publication in the Advances in
Mathematics. Notational change: what was called chi(Gamma) in version 1 is
now called chi(BGamma), and chi(Gamma) now signifies the sum of the
components of the functorial Euler characteristic chi_f(Gamma). Theorem 5.25
summarizes when all Euler characteristics are equal. Minor typos have been
corrected. 88 page
A Computationally Practical Simulation Estimation Algorithm for Dynamic Panel Data Models with Unobserved Endogenous State Variables
This paper develops a simulation estimation algorithm that is particularly useful for estimating dynamic panel data models with unobserved endogenous state variables. The new approach can easily deal with the commonly encountered and widely discussed âinitial conditions problem,â as well as the more general problem of missing state variables during the sample period. Repeated sampling experiments on dynamic probit models with serially correlated errors indicate that the estimator has good small sample properties. We apply the estimator to a model of married womenâs labor force participation decisions. The results show that the rarely used Polya model, which is very difficult to estimate given missing data problems, fits the data substantially better than the popular Markov model. The Polya model implies far less state dependence in employment status than the Markov model. It also implies that observed heterogeneity in education, young children and husband income are much more important determinants of participation, while race is much less important.Initial Conditions, Missing Data, Simulation, Female Labor Force Participation Decisions
A Computationally Practical Simulation Estimation Algorithm for Dynamic Panel Data Models with Unobserved Endogenous State Variables
This paper develops a simulation estimation algorithm that is particularly useful for estimating dynamic panel data models with unobserved endogenous state variables. The new approach can easily deal with the commonly encountered and widely discussed "initial conditions problem," as well as the more general problem of missing state variables during the sample period. Repeated sampling experiments on dynamic probit models with serially correlated errors indicate that the estimator has good small sample properties. We apply the estimator to a model of married women's labor force participation decisions. The results show that the rarely used Polya model, which is very difficult to estimate given missing data problems, fits the data substantially better than the popular Markov model. The Polya model implies far less state dependence in employment status than the Markov model. It also implies that observed heterogeneity in education, young children and husband income are much more important determinants of participation, while race is much less important.simulation, missing data, initial conditions, female labor force participation
Life Cycle Employment and Fertility Across Institutional Environments
In this paper, we formulate a dynamic utility maximization model of female labor force participation and fertility choices and estimate approximate decision rules using data on married women in Italy, Spain and France. The pattern of estimated state dependence effects across countries is consistent with aggregate patterns in part-time employment and child care availability, suggesting that labor market rigidities and lack of child care options are important sources of state dependence. Simulations of the model reveal that Italian and Spanish women would substantially increase their partic- ipation rates were they to face the French institutional environment.Female Employment, Fertility, Child Care, Institutions, Decision Rules
Core hole-electron correlation in coherently coupled molecules
We study the core hole-electron correlation in coherently coupled molecules
by energy dispersive near edge X-ray absorption fine-structure spectroscopy. In
a transient phase, which exists during the transition between two bulk
arrangements, 1,4,5,8-naphthalene-tetracarboxylicacid-dianhydride multilayer
films exhibit peculiar changes of the line shape and energy position of the
X-ray absorption signal at the C K-edge with respect to the bulk and gas phase
spectra. By a comparison to a theoretical model based on a coupling of
transition dipoles, which is established for optical absorption, we demonstrate
that the observed spectroscopic differences can be explained by an
intermolecular delocalized core hole-electron pair. By applying this model we
can furthermore quantify the coherence length of the delocalized core-exciton.Comment: 5 pages, 3 figures, Accepted Version, PRL, minor wording change
Betaine, organic acids and inulin do not affect ileal and total tract nutrient digestibility or microbial fermentation in piglets
The study was conducted to investigate the effects of betaine alone or combined with organic acids and inulin on ileal and total tract nutrient digestibilities and intestinal microbial fermentation characteristics in piglets. In total, 24 four-week-old barrows with an average initial body weight of 6.7 kg were used in two consecutive experiments with 12 piglets each. Betaine, organic acids and inulin at a level of 0.2, 0.4 and 0.2%, respectively, or combinations of these supplements were added to the basal diet. The supplementation of betaine, organic acids and inulin or any of their combinations did not affect ileal and total tract nutrient digestibilities. The microbial fermentation products both at the ileal and faecal level were not affected by any of the treatments. In conclusion, combining betaine with organic acids and inulin did not have any associated effects on the variables that were measured
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