A Semiparametric Time Trend Varying Coefficients Model: With An Application to Evaluate Credit Rationing in U.S. Credit Market

In this paper, we propose a new semiparametric varying coefficient model which extends the existing semi-parametric varying coefficient models to allow for a time trend regressor with smooth coefficient function. We propose to use the local linear method to estimate the coefficient functions and we provide the asymptotic theory to describe the asymptotic distribution of the local linear estimator. We present an application to evaluate credit rationing in the U.S. credit market. Using U.S. monthly data (1952.1-2008.1) and using inflation as the underlying state variable, we find that credit is not rationed for levels of inflation that are either very low or very high. For the remaining values of inflation in the sample, we find that credit is rationed and the Mundell-Tobin effect holds.non-stationarity, semi-parametric smooth coefficients, nonlinearity, credit rationing

Category Reporting in Charitable Giving: An Experimental Analysis

Harbaugh (1998a) has shown theoretically that charities can increase the size of donations by publicly acknowledging their donors using categories. In a complementary paper,using the data on the donations given by 146 lawyers to their almamater law school, Harbaugh (1998b) provided empirical support for this theoretical assertion. Essentially, being acknowledged in categories gives donors some prestige benefits. In this paper, we experimentally investigate the impact of various reporting plans as described in Harbaugh (1998a and 1998b) on the behavior of donors. Our results show that, although the category reporting plan has no significant impact on the size of donations when compared to the exact reporting plan and the no reporting plan, it does signi�ficantly alter the charitable behavior of donors. We show that the presence of a category reporting plan induces the clustering of donations on the lower boundaries of categories, which suggests that donors are motivated by prestige. We also discover that in some circumstances the presence of prestige benefi�ts crowds out the warm glow motive for giving

Spinning particles, axion radiation, and the classical double copy

We extend the perturbative double copy between radiating classical sources in gauge theory and gravity to the case of spinning particles. We construct, to linear order in spins, perturbative radiating solutions to the classical Yang-Mills equations sourced by a set of interacting color charges with chromomagnetic dipole spin couplings. Using a color-to-kinematics replacement rule proposed earlier by one of the authors, these solutions map onto radiation in a theory of interacting particles coupled to massless fields that include the graviton, a scalar (dilaton) $\phi$ and the Kalb-Ramond axion field $B_{\mu\nu}$. Consistency of the double copy imposes constraints on the parameters of the theory on both the gauge and gravity sides of the correspondence. In particular, the color charges carry a chromomagnetic interaction which, in $d=4$, corresponds to a gyromagnetic ratio equal to Dirac's value $g=2$. The color-to-kinematics map implies that on the gravity side, the bulk theory of the fields $(\phi,g_{\mu\nu},B_{\mu\nu})$ has interactions which match those of $d$-dimensional `string gravity,' as is the case both in the BCJ double copy of pure gauge theory scattering amplitudes and the KLT relations between the tree-level $S$-matrix elements of open and closed string theory.Comment: 10+5 pages, LaTeX, 2 figures. v2:Fixed typos and added minor clarification

Gravitational radiation from the classical spinning double copy

We establish a correspondence between perturbative classical gluon and gravitational radiation emitted by spinning sources, to linear order in spin. This is an extension of the non-spinning classical perturbative double copy and uses the same color-to-kinematic replacements. The gravitational theory has a scalar (dilaton) and a 2-form field (the Kalb-Ramon axion) in addition to the graviton. In arXiv:1712.09250, we computed axion radiation in the gravitational theory to show that the correspondence fixes its action. Here, we present complete details of the gravitational computation. In particular, we also calculate the graviton and dilaton amplitudes in this theory and find that they precisely match with the predictions of the double copy. This constitutes a non-trivial check of the classical double copy correspondence, and brings us closer to the goal of simplifying the calculation of gravitational wave observables for astrophysically relevant sources.Comment: 20 pages, 4 figure

Price Increasing Competition? Experimental Evidence

Economic intuition suggests that increased competition generates lower prices. However, recent theoretical work shows that a monopolist may charge a lower price than a firm facing a competitor selling a differentiated product. The direction of the price change when competition is introduced is dependent upon the joint distribution of buyer values for the two products. We explore this relationship using controlled laboratory experiments. Our results indicate that the distribution of buyer values does affect prices in a manner consistent with the theoretical predictions, although price increasing competition is rare due in part to overly intense competition regardless of the distribution of buyer values. We also explore pricing dynamics and find that sellers are more sensitive to their rivals when buyer values are positively correlated.product differentiation, pricing, market structure, market experiments

Deep Short Text Classification with Knowledge Powered Attention

Short text classification is one of important tasks in Natural Language Processing (NLP). Unlike paragraphs or documents, short texts are more ambiguous since they have not enough contextual information, which poses a great challenge for classification. In this paper, we retrieve knowledge from external knowledge source to enhance the semantic representation of short texts. We take conceptual information as a kind of knowledge and incorporate it into deep neural networks. For the purpose of measuring the importance of knowledge, we introduce attention mechanisms and propose deep Short Text Classification with Knowledge powered Attention (STCKA). We utilize Concept towards Short Text (C- ST) attention and Concept towards Concept Set (C-CS) attention to acquire the weight of concepts from two aspects. And we classify a short text with the help of conceptual information. Unlike traditional approaches, our model acts like a human being who has intrinsic ability to make decisions based on observation (i.e., training data for machines) and pays more attention to important knowledge. We also conduct extensive experiments on four public datasets for different tasks. The experimental results and case studies show that our model outperforms the state-of-the-art methods, justifying the effectiveness of knowledge powered attention

Weighted estimation of the dependence function for an extreme-value distribution

Bivariate extreme-value distributions have been used in modeling extremes in environmental sciences and risk management. An important issue is estimating the dependence function, such as the Pickands dependence function. Some estimators for the Pickands dependence function have been studied by assuming that the marginals are known. Recently, Genest and Segers [Ann. Statist. 37 (2009) 2990-3022] derived the asymptotic distributions of those proposed estimators with marginal distributions replaced by the empirical distributions. In this article, we propose a class of weighted estimators including those of Genest and Segers (2009) as special cases. We propose a jackknife empirical likelihood method for constructing confidence intervals for the Pickands dependence function, which avoids estimating the complicated asymptotic variance. A simulation study demonstrates the effectiveness of our proposed jackknife empirical likelihood method.Comment: Published in at http://dx.doi.org/10.3150/11-BEJ409 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Category Reporting in Charitable Giving: An Experimental Analysis

Harbaugh (1998a) has shown theoretically that charities can increase the size of donations by publicly acknowledging their donors using categories. In a complementary paper,using the data on the donations given by 146 lawyers to their almamater law school, Harbaugh (1998b) provided empirical support for this theoretical assertion. Essentially, being acknowledged in categories gives donors some prestige benefits. In this paper, we experimentally investigate the impact of various reporting plans as described in Harbaugh (1998a and 1998b) on the behavior of donors. Our results show that, although the category reporting plan has no significant impact on the size of donations when compared to the exact reporting plan and the no reporting plan, it does signi�ficantly alter the charitable behavior of donors. We show that the presence of a category reporting plan induces the clustering of donations on the lower boundaries of categories, which suggests that donors are motivated by prestige. We also discover that in some circumstances the presence of prestige benefi�ts crowds out the warm glow motive for giving.laboratory experiment; charitable giving; reporting plans; prestige; warm glow