Wage Compression and the Division of Returns to Productivity Growth: Evidence from EOPP

This paper analyzes the relationship between wages and productivity during the early years of an employment relationship. Data from the Employment Opportunity Pilot Project show that worker productivity grows substantially during the first two years on the job, with most of the growth in productivity occurring at the very start of the job. Correcting for measurement error and the fact that expected productivity beyond the start of the job may be folded into the starting wage if wage revisions are not instantaneous, one finds that variation in productivity is only partially reflected in wages. Not only is productivity growth stemming from human capital accumulation while on the job only partially reflected in wage growth, but starting productivity differences for workers in the same job – in large part driven by differences in relevant experience - are only partially reflected in starting wage differences. Our empirical findings can be explained by a simple model of employer – worker cost sharing in which (a) the cost to a worker of locating and moving to a new job increases with the worker's stock of human capital and (b) equity norms prevent employers from paying senior workers lower wages than junior workers who are no more productive.Wages, Productivity, Compression

How Responsive are Quits to Benefits?

It has been argued that one of the functions of fringe benefits is to reduce turnover. However, due to a lack of data, the effect on quits of the marginal dollar of benefits relative to the marginal dollar of wages is an under-researched topic. This paper uses the benefit incidence data in the 1979 Cohort of the National Longitudinal Survey of Youth (NLSY79) and the cost information in the National Compensation Survey to impute benefit costs. The value of imputed benefits is then entered as an explanatory variable in a mobility equation that is estimated using turnover information in the NLSY. We find that the quit rate is much more responsive to fringe benefits than to wages; this is even more the case with total turnover. We also find that benefit costs are correlated with training provision. Due to the high correlation of the costs of individual benefits, it is not possible to disentangle the effects of separate benefits. An interesting feature of the model that we develop for interpreting the strong negative relationship between fringe benefits and turnover is that abstracting from heterogeneity, workers must at the margin place a higher valuation on a dollar of wages than a dollar of benefits since otherwise an employer could profit by switching compensation from wages to fringes. Worker heterogeneity modifies this result and reinforces any causal relationship between fringe benefits and turnover provided that more stable workers have a greater preference for compensation in the form of fringes.Turnover, Fringe Benefits

Baikov-Lee Representations Of Cut Feynman Integrals

We develop a general framework for the evaluation of $d$-dimensional cut Feynman integrals based on the Baikov-Lee representation of purely-virtual Feynman integrals. We implement the generalized Cutkosky cutting rule using Cauchy's residue theorem and identify a set of constraints which determine the integration domain. The method applies equally well to Feynman integrals with a unitarity cut in a single kinematic channel and to maximally-cut Feynman integrals. Our cut Baikov-Lee representation reproduces the expected relation between cuts and discontinuities in a given kinematic channel and furthermore makes the dependence on the kinematic variables manifest from the beginning. By combining the Baikov-Lee representation of maximally-cut Feynman integrals and the properties of periods of algebraic curves, we are able to obtain complete solution sets for the homogeneous differential equations satisfied by Feynman integrals which go beyond multiple polylogarithms. We apply our formalism to the direct evaluation of a number of interesting cut Feynman integrals.Comment: 37 pages; v2 is the published version of this work with references added relative to v

Thermal Stress on Intertidal Limpets: Long-Term Hindcasts and Lethal Limits

When coupled with long-term meteorological records, a heat-budget model for the limpet, Lottia gigantea, provides a wealth of information regarding environmental and topographic controls of body temperature in this ecologically important species. (1) The maximum body temperature predicted for any site (37.5°C) is insufficient to kill all limpets, suggesting that acute thermal stress does not set an absolute upper limit to the elevation of L. gigantea on the shore. Therefore, the upper limit must be set by behavioral responses, sublethal effects or ecological interactions. (2) Temperatures sufficient to kill limpets are reached at only a small fraction of substratum orientations and elevations and on only three occasions in 5 years. These rare predicted lethal temperatures could easily be missed in field measurements, thereby influencing the interpretation of thermal stress. (3) Body temperature is typically higher than air temperature, but maximum air temperature can nonetheless be used as an accurate predictor of maximum body temperature. Warmer air temperatures in the future may thus cause increased mortality in this intertidal species. Interpretation of the ecological effects of elevated body temperature depends strongly on laboratory measurements of thermal stress, highlighting the need for additional research on the temporal and spatial variability of thermal limits and sublethal stress. The lengthy time series of body temperatures calculated from the heat-budget model provides insight into how these physiological measurements should be conducted

Multiparton webs in non-abelian gauge theories at three loops and beyond

Amplitudes in theories with a massless gauge boson suffer from so-called infrared divergences where off-shell states become asymptotically close to the mass-shell in loop or phase-space momentum integrals. These singularities have been shown to cancel intricately order-by-order in the perturbative expansion. However, in order to obtain meaningful and precise predictions for physical observables, we must understand and compute such divergences to high orders. This can be accomplished by calculating webs: weighted sets of Feynman diagrams which, when exponentiated give the complete infrared singular component of the amplitude, known as the soft function. This quantity is formally equivalent to a vacuum expectation value of a product of Wilson lines. In this thesis we shall study webs correlating multiple Wilson lines, which differs from the two line case due to the possibility of non-trivial colour flows. This renders the soft function matrix valued in the space of colour flows, thus making its calculation and renormalisation non-trivial. At present, the infrared singularities of non-abelian, multiparton scattering amplitudes are known only to two loops in general kinematics, and to three loops in a simplifying kinematic limit. This thesis will thus form part of a program of work aimed at calculating and understanding the three-loop singularities in general kinematics and in doing so we aim to gain all-order insights into the pertubative structure of non-abelian gauge theories. We first specialise to a subset of webs which we have called Multiple Gluon Exchange Webs (MGEWs), which contain only those diagrams with direct exchanges of soft gauge bosons directly between Wilson lines with no intervening three- or four- boson vertices. Studing their properties allows us to construct a basis of functions which describes all examples of such webs, and we conjecture will continue to do so at any order. Furthermore, we find that the basis functions can be described by a simple, one-dimensional integral over only logarithms. We go on to compute several examples providing evidence for the validity of our basis and demonstrate the utility of the framework we have built by computing a four-loop web and providing some all-order results for particular classes of MGEW. We then consider a step beyond MGEWs, that is, webs which contain a single three-gluon vertex sub-diagram. In particular we study the simplest web in this class correlating four lines at three loops and attempt to calculate it through the numerical fitting of a physically motivated ansatz. We show that this web cannot carry kinematic dependence through conformal invariant cross ratios, which arise when connected subdiagrams correlate at least four lines. Hence, it is subject to the same constraints as MGEWs with regards to their symbol alphabet, from the physical considerations in their lightlike limit and spacelike/timelike analytic continuation. Like all other known webs satisfying such constraints, we therefore argue that it can be written in terms of sums of products of MGEW basis functions. Symmetries inherent to our parameterisation of the cusp angles, Bose symmetry and transcendental weight further constrain this ansatz, resulting in forty parameters for which we present preliminary results of a numerical fit

Undergraduate Education Students’ Perceptions of Effective and Ineffective Course Experiences: What Counts as an Effective Experience?

Pre-service teachers’ conceptions of effective and ineffective instruction stand to inform their personal views of what constitutes effective and ineffective instruction, yet few qualitative studies have examined both conceptions of effective and ineffective instruction. The purpose of this study was to determine whether pre-service teachers described what happens in university courses primarily in terms of teacher characteristics, teaching practices, or instructional context. There were two research questions guiding the study. First, how are the dimensions of effective and ineffective instruction alike and different? Second, how do results correspond to similar qualitative studies? Nine distinct themes were inductively derived through open coding of 34 pre-service teachers’ essays: (a) motivation, (b) student autonomy, (c) meaningful learning, (d) comfortable learning environment, (e) classroom management, (f) student-teacher relationship, (g) teacher’s personal characteristics and manner, (h) lesson organization, and (i) teacher impact/student development. The results of this study support previous findings and add to the small number of studies that have examined pre-service teachers' descriptions of effective and ineffective instruction. Findings have also contributed a new category that has not appeared in previous literature: teacher impact/student development. Pre-service teachers’ descriptions in this study confirm that the theoretical conception of what happens in classrooms must include the teacher’s characteristics, teaching, and the context of instruction. Keywords: education theory and practice, educational psychology, higher education, teacher education, pre-service teacher beliefs, pre-service teacher conceptions, effective instruction, effective teaching. Les conceptions qu’ont les enseignants en formation de l’enseignement efficace et inefficace informent naturellement leurs points de vue personnels de ce qui constitue l’enseignement efficace et inefficace; pourtant, peu d’études qualitatives se sont penchées sur les conceptions de l’enseignement efficace ainsi que sur celles de l’enseignement inefficace. L’objectif de cette étude était de déterminer dans quelle mesure les enseignants en formation décrivent ce qui se passe dans les cours à l’université, notamment en fonction des caractéristiques des enseignants, des pratiques d’enseignement ou du contexte pédagogique. Deux questions ont guidé la recherche. D’abord, qu’est-ce que l’enseignement efficace et l’enseignement inefficace ont en commun et qu’est-ce qui les distingue? Deuxièmement, comment les résultats correspondent-ils à ceux d’études qualitatives similaires? Un codage ouvert de 34 dissertations écrites par des enseignants en formation a permis de recueillir, par induction, neuf thèmes distincts: (a) motivation, (b) autonomie des étudiants, (c) apprentissage significatif, (d) milieu d’apprentissage confortable, (e) gestion de la classe, (f) rapport étudiant-enseignant, (g) caractéristiques et manières personnelles de l’enseignant, (h) organisation des leçons, et (i) impact de l’enseignant/progression des étudiants. Les résultats de cette étude appuient ceux des études antérieures. Cette étude élargit le nombre restreint d’études qui ont porté sur les descriptions par des enseignants en formation de l’enseignement efficace et l’enseignement inefficace. Les résultats contribuent également à une nouvelle catégorie qui n’apparait pas dans les travaux antérieurs : impact de l’enseignant/progression des étudiants. Les descriptions par les enseignants en formation qui ont participé à cette étude confirment la conception théorique selon laquelle ce qui arrive dans la salle de classe doit tenir compte des caractéristiques personnelles de l’enseignant, de l’enseignement et du contexte pédagogique. Mots clés : théorie et pratique en éducation, psychologie de l’éducation; études supérieures, formation des enseignants; croyances des enseignants en formation, conceptions des enseignants en formation, enseignement efficac

A CASE STUDY ON THE EFFECTS OF THE UPPER ARM DEFINITION ON SHOULDER AND ELBOW KINEMATICS DURING THE BADMINTON SMASH

The aim of this case study was to identify the effect of the upper arm definition on shoulder and elbow kinematics during the badminton smash. A method was proposed that corrects the false external rotation when using the shoulder-elbow-wrist plane based on the carrying angle (ISB-2C) and compared to ISB recommendations for defining the upper arm (ISB-1 and ISB-2). Differences were found in shoulder and elbow kinematics, in particular angular velocities. Both magnitude and the time history of the angular velocity were affected. In particular, use of the medial and lateral epicondyles was unable to detect a reasonable signal for pronation/supination. ISB-2C reduces some of the problems associated with ISB-1 and ISB-2 e.g. soft-tissue artifact, proximity of medial and lateral epicondyles to the humeral longitudinal axis and false external rotation caused by the carrying angle

RELATIONSHIPS BETWEEN WHOLE-BODY KINEMATICS AND BADMINTON JUMP SMASH RACKET HEAD SPEED

The purpose of this study was to identify kinematic determinants of shuttlecock speed in the badminton jump smash. Three-dimensional kinematic (400 Hz) data were collected for 18 experienced male badminton players using an 18 camera Vicon Motion Analysis System. Each participant performed 12 jump smashes. The trial with the fastest shuttlecock speed per participant was analysed using an 18-segment rigid body model. Parameters were calculated describing elements of the badminton jump smash technique. Four kinematic variables were significantly correlated with racket head speed. Greater peak wrist joint centre linear velocity, jump height, shorter acceleration phase, and greater shoulder internal rotation at shuttlecock / racket impact