Heteroscedasticity and non-monotonic efficiency effects of a stochastic frontier model

We consider a model that provides flexible parameterizations of the exogenous influences on inefficiency. In particular, we demonstrate the model's unique property of accommodating non-monotonic efficiency effect. With this non-monotonicity, production efficiency no longer increases or decreases monotonically with the exogenous influence; instead, the relationship can shifts within the sample. Our empirical example shows that variables can indeed have non-monotonic effects on efficiency. Furthermore, ignoring non-monotonicity is shown to yield an inferior estimation of the model, which sometimes results in opposite predictions concerning the data.stochastic frontiers; heteroscedasticity; non-monotonic effects

Symmetrical Information and Credit Rationing: Graphical Demonstrations

As this article shows, the pro-debtor U.S. Bankruptcy Code alone can cause credit rationing, even without asymmetrical information in the market, because the code entails substantial costs to lenders if borrowers file for bankruptcy. In the absence of bankruptcy cost, lenders are always justified in raising interest rates and clearing markets. If the bankruptcy cost is nontrivial, however, lenders' profits are concave in the relevant range of interest rates. Thus, lenders cannot always clear the market by using higher rates. The study reported here also found that the use of collateral in debt contracts can reduce rationing but that even 100 percent collateral does not eliminate all rationing possibilities. A positive relationship was found between credit risk and the amount of pledged collateral, which is not necessarily true with models based on asymmetrical information.Company Failures; Credit Control; Debt

Character formulae in category O\mathcal O for exceptional Lie superalgebra G(3)G(3)

We classify the blocks, compute the Verma flags of tilting and projective modules in the BGG category $\mathcal O$ for the exceptional Lie superalgebra $G(3)$. The projective injective modules in $\mathcal O$ are classified. We also compute the Jordan-H\"older multiplicities of the Verma modules in $\mathcal O$.Comment: 28 page

Brundan-Kazhdan-Lusztig and super duality conjectures

We formulate a general super duality conjecture on connections between parabolic categories O of modules over Lie superalgebras and Lie algebras of type A, based on a Fock space formalism of their Kazhdan-Lusztig theories which was initiated by Brundan. We show that the Brundan-Kazhdan-Lusztig (BKL) polynomials for Lie superalgebra gl(m|n) in our parabolic setup can be identified with the usual parabolic Kazhdan-Lusztig polynomials. We establish some special cases of the BKL conjecture on the parabolic category O of gl(m|n)-modules and additional results which support the BKL conjecture and super duality conjecture.Comment: v2, 44 pages, mild changes, clarifications on Introduction and other place

Equivalence of blocks for the general linear Lie superalgebra

We develop a reduction procedure which provides an equivalence (as highest weight categories) from an arbitrary block (defined in terms of the central character and the integral Weyl group) of the BGG category O for a general linear Lie superalgebra to an integral block of O for (possibly a direct sum of) general linear Lie superalgebras. We also establish indecomposability of blocks of O.Comment: Formulation of Theorem 2.1 fixed in the last versio

One-step and two-step estimation of the effects of exogenous variables on technical efficiency levels

Consider a stochastic frontier model with one-sided inefficiency u, and suppose that the scale of u depends on some variables (firm characteristics) z. A one-step model specifies both the stochastic frontier and the way in which u depends on z, and can be estimated in a single step, for example by maximum likelihood. This is in contrast to a two-step procedure, where the first step is to estimate a standard stochastic frontier model, and the second step is to estimate the relationship between (estimated) u and z. In this paper we propose a class of one-step models based on the scaling property that u equals a function of z times a one-sided error u * whose distribution does not depend on z. We explain theoretically why two-step procedures are biased, and we present Monte Carlo evidence showing that the bias can be very severe. This evidence argues strongly for one-step models whenever one is interested in the effects of firm characteristics on efficiency levels.technical efficiency; stochastic frontiers

Brundan-Kazhdan-Lusztig conjecture for general linear Lie superalgebras

In the framework of canonical and dual canonical bases of Fock spaces, Brundan in 2003 formulated a Kazhdan-Lusztig type conjecture for the characters of the irreducible and tilting modules in the BGG category for the general linear Lie superalgebra for the first time. In this paper, we prove Brundan's conjecture and its variants associated to all Borel subalgebras in full generality.Comment: 64 pages, Notes in the Introduction and Remark 3.14 adde