The Effect of Technology Choice on Automobile Assembly Plant Productivity

Productivity growth is usually represented by a continuous shift of the production or cost function. In the automobile industry, there is evidence of a more discrete change in the technology. I estimate a structural model of production and technology choice, using a panel of US automobile assembly plants from 1963 to 1996. New decomposition results suggest that plant-level changes, as opposed to compositional effects, are the most important determinant of aggregate productivity growth.

Measurement of Chronic and Transient Poverty: Theory and Application to Pakistan

This paper investigates how to characterize each person's poverty status when his/her welfare level fluctuates and how to aggregate the status into chronic and transient poverty measures. The contribution of the paper is to clarify the sensitivity of relative magnitudes of chronic versus transient poverty to the choice of a poverty measure. We show this by theoretically re-examining Ravallion's (1988) decomposition of the expected value of a poverty measure into chronic and transient components. The examination covers major poverty measures including those developed by Foster et al. (1985), which are used extensively in the existing studies. Our analysis shows that the chronic-transient decomposition using the squared poverty gap index might be too sensitive to the poverty line and that the index is justified only if we accept that the welfare cost of consumption fluctuation is independent of the depth of chronic poverty. If we instead believe that the decomposition should not be too sensitive to the poverty line and that the welfare cost of risk is more severe when an individual's chronic poverty is deeper, other poverty measures such as suggested by Clark et al. (1981) are useful. We also investigate how empirically different are the relative magnitudes of chronic versus transient poverty, depending on the choice of a poverty measure. Based on a two-period household panel dataset collected in Pakistan, we show that the difference is substantial even when the poorest experienced only a small fluctuation in their consumption.chronic poverty, transient poverty, risk, poverty measurement

Koszul gradings on Brauer algebras

We show that the Brauer algebra over the complex numbers for an integral parameter delta can be equipped with a grading, in the case of delta being non-zero turning it into a graded quasi-hereditary algebra. In which case it is Morita equivalent to a Koszul algebra. This is done by realizing the Brauer algebra as an idempotent truncation of a certain level two VW-algebra for some large positive integral parameter N. The parameter delta appears then in the choice of a cyclotomic quotient. This cyclotomic VW-algebra arises naturally as an endomorphism algebra of a certain projective module in parabolic category O for an even special orthogonal Lie algebra. In particular, the graded decomposition numbers are given by the associated parabolic Kazhdan-Lusztig polynomials.Comment: 28 page

Hecke algebras, modular categories and 3-manifolds quantum invariants

We construct modular categories from Hecke algebras at roots of unity. For a special choice of the framing parameter, we recover the Reshetikhin-Turaev invariants of closed 3-manifolds constructed from the quantum groups U_q sl(N) by Reshetikhin-Turaev and Turaev-Wenzl, and from skein theory by Yokota. We then discuss the choice of the framing parameter. This leads, for any rank N and level K, to a modular category \tilde H^{N,K} and a reduced invariant \tilde\tau_{N,K}. If N and K are coprime, then this invariant coincides with the known PSU(N) invariant at level K. If gcd(N,K)=d>1, then we show that the reduced invariant admits spin or cohomological refinements, with a nice decomposition formula which extends a theorem of H. Murakami.Comment: 32 pages. See also http://www.math.sciences.univ-nantes.fr/~blanche

A conjecture for q-decomposition matrices of cyclotomic v-Schur algebras

The Jantzen sum formula for cyclotomic v-Schur algebras yields an identity for some q-analogues of the decomposition matrices of these algebras. We prove a similar identity for matrices of canonical bases of higher-level Fock spaces. We conjecture then that those matrices are actually identical for a suitable choice of parameters. In particular, we conjecture that decomposition matrices of cyclotomic v-Schur algebras are obtained by specializing at q=1 some transition matrices between the standard basis and the canonical basis of a Fock space.Comment: This is the final version (published version). No new result since Version 2, but major changes of the organization of the paper and the results. Some proofs and sections rewritten. References added and correcte

Bounded Learning Efficiency and Sources of Firm Level Productivity Growth in Colombian Food Manufacturing Industry

The measurement of productivity fluctuations has been the focus of decades-long interest. In addition to broad structural forces driving productivity changes, there is more recent interest in measuring and identifying the heterogeneous forces driving these changes. A major force is learning-by-doing which is used by economists to describe the phenomenon of productivity growth arising from the accumulation of production experience by a firm. This paper proposes a bounded learning concept with the learning progress function characterized by the degree of efficiency and the specification of the learning progress as a logistic function capturing both the slow start-up and the limit in learning progress. The inter-firm learning inefficiency is defined as the inability of a firm to reach the optimal plateau relative to the ‘best practice’ firm from the set of comparable firms. We further differentiate learning efficiency from the technical efficiency. The key contribution of this research is to provide a measure the firm’s movement along the learning progress curve and explain the existence of firm-level heterogeneity in learning. The time varying technical efficiency is estimated based on stochastic production frontier methods and firm-specific learning efficiency is disentangled using the residual of the production frontier (productivity).The model is then used to decompose the factor productivity growth into components associated with learning, scale, technical efficiency, technological change and change in allocative efficiency. This productivity growth decomposition provides useful information and policy level insight in firm-level productivity analysis. The major econometric issue in production function estimation is the possibility that there are some forces influencing production that are only observed by the firm and not by the econometrician. With firm input use being endogenous, inputs might be correlated with unobserved productivity shocks. The measure of technical efficiency by estimating the production frontier directly in presence of endogeneity of input choice can be biased in the sense that the measure of efficiency favors the firms employing higher levels of inputs. The Levinsohn and Petrin (2003) approach is extended to overcome this simultaneity problem in stochastic production frontier estimation to generate consistent estimates of production parameters and technical efficiency. The model is applied to plant-level panel data on Colombian food manufacturing sector. The dataset is unique longitudinal data on firms in the sense that it has information on both plant-specific physical quantities and prices for both outputs and inputs. In contrast to most of the existing literature which measure productivity by deflating sales by an industry-level price index, these data eliminate a common source of measurement error in production function estimation. Plant-level productivity growth decomposition and the contribution of learning effect are explored by estimating the production frontier and firm-specific learning efficiency.Colombian food manufacturing industry, Bounded learning-by-doing, Learning efficiency, Logistic differential equation, Technical efficiency, Firm-level productivity growth, Decomposition of productivity change, Endogeneity of input choice, Stochastic production frontier, Agribusiness, Industrial Organization, Production Economics, Productivity Analysis,

Gauge-independence of gluon spin in the nucleon and its evolution

In recent papers, we have established the existence of gauge-invariant decomposition of nucleon spin, each term of which can be related to known high-energy deep-inelastic-scattering observables. A subtlety remains, however, for the intrinsic spin part of gluons at the quantum level. In fact, it was sometimes claimed that the evolution of gluon spin depends on the gauge choice and its physical interpretation makes sense only in the light-cone gauge. In the present paper, we will demonstrate explicitly that the gluon spin operator appearing in our decomposition evolves gauge-independently and that it properly reproduces the familiar evolution equation for the 1st moments of polarized quark and gluon distributions obtained with the Altarelli-Parisi method, which cannot directly be checked by the standard operator expansion method.Comment: The version accepted for publication in Physical Review

On the equivalence of strong formulations for capacitated multi-level lot sizing problems with setup times

Several mixed integer programming formulations have been proposed for modeling capacitated multi-level lot sizing problems with setup times. These formulations include the so-called facility location formulation, the shortest route formulation, and the inventory and lot sizing formulation with (l,S) inequalities. In this paper, we demonstrate the equivalence of these formulations when the integrality requirement is relaxed for any subset of binary setup decision variables. This equivalence has significant implications for decomposition-based methods since same optimal solution values are obtained no matter which formulation is used. In particular, we discuss the relax-and-fix method, a decomposition-based heuristic used for the efficient solution of hard lot sizing problems. Computational tests allow us to compare the effectiveness of different formulations using benchmark problems. The choice of formulation directly affects the required computational effort, and our results therefore provide guidelines on choosing an effective formulation during the development of heuristic-based solution procedures

Measuring Semantic Similarity by Latent Relational Analysis

This paper introduces Latent Relational Analysis (LRA), a method for measuring semantic similarity. LRA measures similarity in the semantic relations between two pairs of words. When two pairs have a high degree of relational similarity, they are analogous. For example, the pair cat:meow is analogous to the pair dog:bark. There is evidence from cognitive science that relational similarity is fundamental to many cognitive and linguistic tasks (e.g., analogical reasoning). In the Vector Space Model (VSM) approach to measuring relational similarity, the similarity between two pairs is calculated by the cosine of the angle between the vectors that represent the two pairs. The elements in the vectors are based on the frequencies of manually constructed patterns in a large corpus. LRA extends the VSM approach in three ways: (1) patterns are derived automatically from the corpus, (2) Singular Value Decomposition is used to smooth the frequency data, and (3) synonyms are used to reformulate word pairs. This paper describes the LRA algorithm and experimentally compares LRA to VSM on two tasks, answering college-level multiple-choice word analogy questions and classifying semantic relations in noun-modifier expressions. LRA achieves state-of-the-art results, reaching human-level performance on the analogy questions and significantly exceeding VSM performance on both tasks