Can Union Labor Ever Cost Less?

This paper examines the effect of unions on efficiency by estimating cost function systems over three different sets of construction projects. The results show that union contractors have greater economies of scale. This gives them a cost advantage in large commercial office buildings, but in school and hospital construction, nonunion contractors have lower costs at all output levels. Despite the cost differences, profits for nonunion contractors in school and hospital construction are no higher than those for union contractors because the burden of higher union costs is shifted to buyers.

Human Resource Policies and Union-Nonunion Productivity Differences

Many researchers in both economics departments and business schools recently have become interested in examining how much of an effect human resource decisions and policies have on firm performance. This paper surveys the literature on unionism and productivity and discusses its implications for future research on more general issues. The main focus is on (I) conclusions as to whether unions raise or lower productivity and (2) procedures used to identify the channels through which unions affect productivity. The studies of unions and productivity have documented large productivity differences between seemingly comparable union and nonunion establishments. In many cases unionism is associated with higher productivity, especially when unionized firms are in a competitive environment. However, the mechanisms responsible for union-nonunion productivity differences in each study remain poorly understood, either because detailed information on how unions affected company decisions was not available or because the available information produced inconclusive results. These conclusions suggest that human resource policies can have a very large effect on financial outcomes, but our ability to estimate the magnitude of that effect for a particular policy is currently very limited.

Unions and Efficiency in Private Sector Construction: Further Evidence

Previous studies using micro data to estimate the impact of unions on productivity in construction in the early 1970's have found productivity to be higher for union than nonunion contractors in the private sector. The validity of these studies has been questioned in light of the declining market share of union contractors. This study re-examines union-nonunion productivity differences over a sample of retail stores and shopping centers built in the late 1970's. It finds that square footage put in place per hour is 51 percent greater for union than nonunion contractors. Lacking data on wage rates by occupation, the impact of unions on efficiency can be gauged only by looking at how unions affect costs, profit rates, and prices. This study finds no mean cost per square foot difference between union and nonunion contractors and offers mixed econometric evidence on translog cost functions. There is no difference in profit rates or prices between union and nonunion contractors in this sample.

Additional Records of Michigan Bat Ectoparasites

New Michigan county records for Ischnopsyllidae, Cimicidae, Spinturnicidae, Macro- nyssidae, and Trombiculidae from bats are given along with two new bat/parasite records for the United States

Constraining Dark Energy with X-ray Galaxy Clusters, Supernovae and the Cosmic Microwave Background

We present new constraints on the evolution of dark energy from an analysis of Cosmic Microwave Background, supernova and X-ray galaxy cluster data. Our analysis employs a minimum of priors and exploits the complementary nature of these data sets. We examine a series of dark energy models with up to three free parameters: the current dark energy equation of state w_0, the early time equation of state w_et and the scale factor at transition, a_t. From a combined analysis of all three data sets, assuming a constant equation of state and that the Universe is flat, we measure w_0=-1.05+0.10-0.12. Including w_et as a free parameter and allowing a_t to vary over the range 0.5<a_t<0.95 where the data sets have discriminating power, we measure w_0=-1.27+0.33-0.39 and w_et=-0.66+0.44-0.62. We find no significant evidence for evolution in the dark energy equation of state parameter with redshift. Marginal hints of evolution in the supernovae data become less significant when the cluster constraints are also included in the analysis. The complementary nature of the data sets leads to a tight constraint on the mean matter density, Omega_m and alleviates a number of other parameter degeneracies, including that between the scalar spectral index n_s, the physical baryon density Omega_bh^2 and the optical depth tau. This complementary nature also allows us to examine models in which we drop the prior on the curvature. For non-flat models with a constant equation of state, we measure w_0=-1.09+0.12-0.15 and Omega_de=0.70+-0.03. Our analysis includes spatial perturbations in the dark energy fluid, assuming a sound speed c_s^2 =1. For our most general dark energy model, not including such perturbations would lead to spurious constraints on w_et which would be tighter by approximately a factor two with the current data. (abridged)Comment: 11 pages, 13 figures, 2 tables. Accepted for publication in MNRAS. Two new figures added: Fig.9 shows the effects of including dark energy perturbations and Fig.10 compares X-ray cluster data with 2dF dat

Knowledge-based segmentation of SAR data with learned priors

©2000 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or distribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.DOI: 10.1109/83.821747An approach for the segmentation of still and video synthetic aperture radar (SAR) images is described in this note. A priori knowledge about the objects present in the image, e.g., target, shadow, and background terrain, is introduced via Bayes' rule. Posterior probabilities obtained in this way are then anisotropically smoothed, and the image segmentation is obtained via MAP classifications of the smoothed data. When segmenting sequences of images, the smoothed posterior probabilities of past frames are used to learn the prior distributions in the succeeding frame. We show with examples from public data sets that this method provides an efficient and fast technique for addressing the segmentation of SAR data

Pensions and Firm Performance

This paper examines how pension plans affect employee behavior and firm performance. Theoretically, the impact of pensions on firm performance cannot be predicted. Firms with pensions should have lower turnover rates and more efficient retirement decisions; their employees will be less likely to shirk. On the other hand, pension compensation is not very closely linked to worker performance and there is some risk that turnover may fall too much. The evidence indicates that although wages do not seem to fall with pension compensation, profit rates are not affected by pension coverage. This suggests that pension coverage is associated with higher productivity, a proposition that is supported by indirect evidence on pensions, turnover, and productivity but not by direct tests of how pension coverage and productivity are correlated.