Union and Union Threat Premiums Among Graduate Student Stipends

To inform the ongoing debate over graduate student unionization, the author tests for the presence of union-related premiums among teaching and research assistant stipends using data from The Chronicle of Higher Education’s survey of departments in six fields in 2000, 2001, and 2003. Ordinary least squares and instrumental variables methods reveal union and union threat premiums among teaching assistant stipends. There is little evidence of union-related premiums among research assistant stipends. Specifications controlling for union composition or using employment weights reveal that the teaching assistant only union premium is positive for teaching assistant stipends and negative for research assistant stipends. This suggests that collectively bargained contracts may yield benefits for teaching assistants at the expense of research assistants when the latter are excluded from the bargaining unit. There is a positive premium to joint teaching and research assistant unions for teaching assistant stipends and no effect for research assistant stipends

The Effect of Unions on Productivity in the Public Sector: The Case of Municipal Libraries

[Excerpt] This paper represents our initial efforts at analyzing the effects of unions on productivity in the public sector. We first sketch an analytical framework that can be used to estimate these effects, focusing for expository purposes on municipal public libraries. We initially focus on libraries because considerable effort has been devoted to conceptualizing productivity measures for them and because of the availability of data to implement the framework. After discussing the analytical framework, we present preliminary estimtes of the effects of unions on productivity in public libraries based upon analyses of data from 71 municipal libraries in Massachusetts. We conclude by indicating how these analyses will be extended and the direction that we hope our future research will take

Model-robust regression and a Bayesian ``sandwich'' estimator

We present a new Bayesian approach to model-robust linear regression that leads to uncertainty estimates with the same robustness properties as the Huber--White sandwich estimator. The sandwich estimator is known to provide asymptotically correct frequentist inference, even when standard modeling assumptions such as linearity and homoscedasticity in the data-generating mechanism are violated. Our derivation provides a compelling Bayesian justification for using this simple and popular tool, and it also clarifies what is being estimated when the data-generating mechanism is not linear. We demonstrate the applicability of our approach using a simulation study and health care cost data from an evaluation of the Washington State Basic Health Plan.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS362 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

A Fast Algorithm for Robust Regression with Penalised Trimmed Squares

The presence of groups containing high leverage outliers makes linear regression a difficult problem due to the masking effect. The available high breakdown estimators based on Least Trimmed Squares often do not succeed in detecting masked high leverage outliers in finite samples. An alternative to the LTS estimator, called Penalised Trimmed Squares (PTS) estimator, was introduced by the authors in \cite{ZiouAv:05,ZiAvPi:07} and it appears to be less sensitive to the masking problem. This estimator is defined by a Quadratic Mixed Integer Programming (QMIP) problem, where in the objective function a penalty cost for each observation is included which serves as an upper bound on the residual error for any feasible regression line. Since the PTS does not require presetting the number of outliers to delete from the data set, it has better efficiency with respect to other estimators. However, due to the high computational complexity of the resulting QMIP problem, exact solutions for moderately large regression problems is infeasible. In this paper we further establish the theoretical properties of the PTS estimator, such as high breakdown and efficiency, and propose an approximate algorithm called Fast-PTS to compute the PTS estimator for large data sets efficiently. Extensive computational experiments on sets of benchmark instances with varying degrees of outlier contamination, indicate that the proposed algorithm performs well in identifying groups of high leverage outliers in reasonable computational time.Comment: 27 page

Occupationa pensions, wages and tenure wage profiles

Using data from the BHPS, we estimate the impact of occupational pensions on wages and on the tenure profile of wages of male private sector workers in the UK. According to the theoretical literature, occupational pensions participants should receive a premium at the beginning of their careers, when the financial quit disincentives stemming from defined benefit plans are less binding. Our empirical evidence is consistent with this prediction. We find that occupational pension participants earn a positive wage premium only at the beginning of the career. Once we account for the endogenous sorting of individuals into occupational pension schemes, the magnitude of the estimated premium decreases sharply and it looses statistical significance. Indeed, the wage premium appears to be completely explained by unobservable individual and job match heterogeneity

Pennies from Heaven? Using Exogeneous Tax Variation to Identify Effects of School Resources on Pupil Achievements

Despite important policy implications associated with the allocation of education resources, evidence on the effectiveness of school inputs remains inconclusive. In part, this is due to endogenous allocation; families sort themselves non-randomly into school districts and school districts allocate money based in order to compensate (or reinforce) differences in child abilities, which leaves estimates of school input effects likely to be biased. Using variation in education expenditures induced by the location of natural resources in Norway we examine the effect of school resources on pupil outcomes. We find that higher school expenditures, triggered by higher revenues from local taxes on hydropower plants, have a significantly positive effect on pupil performance at age 16. The positive IV estimates contrast with the standard cross-sectional estimates that reveal no effects of extra resources.pupil achievement, school resources