MULTIPLE COMPARISONS WITH THE BEST: BAYESIAN PRECISION MEASURES OF EFFICIENCY RANKINGS

A large literature exists on measuring the allocative and technical efficiency of a set of firms. A segment of this literature uses data envelopment analysis (DEA), creating relative efficiency rankings that are nonstochastic and thus cannot be evaluated according to the precision of the rankings. A parallel literature uses econometric techniques to estimate stochastic production frontiers or distance functions, providing at least the possibility of computing the precision of the resulting efficiency rankings. Recently, Horrace and Schmidt (2000) have applied sampling theoretic statistical techniques known as multiple comparisons with control (MCC) and multiple comparisons with the best (MCB) to the issue of measuring the precision of efficiency rankings. This paper offers a Bayesian multiple comparison alternative that we argue is simpler to implement, gives the researcher increased exibility over the type of comparison made, and provides greater, and more in-tuitive, information content. We demonstrate this method on technical efficiency rankings of a set of U.S. electric generating firms derived within a distance function framework.Research Methods/ Statistical Methods,

The Effects of Children's Time Use and Home and Neighborhood Quality on their Body Weight and Cognitive/Behavioral Development

We estimate a directional distance function to assess the impacts of multiple time-varying parent and child inputs on a cluster of jointly produced child outcomes for children aged 7 to 13 years. The directional distance function specification avoids several well-known empirical problems associated with analysis of household production data, namely, the need to aggregate inputs and outputs, assume separability among inputs and outputs, or estimate reduced form equations. Using a balanced panel of families from the National Longitudinal Survey of Youth-Child Sample for 1996 to 2000, we assess the marginal contributions of home and neighborhood environmental quality and children's time allocations, on their math and reading performance, behavior problems, and body mass index. We also measure productivity growth, technical change, efficiency change, and technical efficiency for production of child outcomes. Our results indicate significant jointness among good and bad child outcomes. Significant improvements in children's good outcomes and reductions in bad outcomes are also associated with a better home and parent perceived neighborhood environment, Head Start participation, and increased family time spent together during meals. Children's productivity growth is found to be highest at age 8 years and diminishes thereafter.Health Economics and Policy, Labor and Human Capital,

The Economics of a Centralized Judiciary: Uniformity, Forum Shopping and the Federal Circuit

In 1982, the US Congress established the Court of Appeals for the Federal Circuit (CAFC) as the sole appellate court for patent cases. Ostensibly, this court was created to eliminate inconsistencies in the application and interpretation of patent law across federal courts, and thereby mitigate the incentives of patentees and alleged infringers to "forum shop" for a preferred venue. We perform the first econometric study of the extent of non-uniformity and forum shopping in the pre-CAFC era and of the CAFC's impact on these phenomena. We find that in patentee-plaintiff cases the pre-CAFC era was indeed characterized by significant non-uniformity in patent validity rates across circuits and by forum shopping on the basis of validity rates. We find weak evidence that the CAFC has increased uniformity of validity rates and strong evidence that forum shopping on the basis of validity rates ceased several years prior to the CAFC's establishment. In patentee-defendant cases, we find that validity rates are lower on average, but do not find either significant non-uniformity of validity rates across circuits or significant forum shopping.

OH yields from the CH3CO+O-2 reaction using an internal standard

Laser flash photolysis of CH3C(O)OH at 248 nm was used to create equal zero time yields of CH3CO and OH. The absolute OH yield from the CH3CO + O2 (+M) reaction was determined by following the OH temporal profile using the zero time OH concentration as an internal standard. The OH yield from CH3CO + O2 (+M) was observed to decrease with increasing pressure with an extrapolated zero pressure yield close to unity (1.1 ± 0.2, quoted uncertainties correspond to 95% confidence limits). The results are in quantitative agreement with those obtained from 248 nm acetone photolysis in the presence of O2

Biochar: an improver of nutrient and soil water availability - what is the evidence?

Biochar has consistently been proposed as a way of improving soil fertility by increasing nutrient and soil water availability. This review critically investigates recent literature, focussing particularly on these agronomic aspects of biochar. We clarify the differences between biochar made from plant (plant derived biochar, PDB) and animal feedstock (animal derived biochar, ADB) and show how pyrolysis temperature affects biochar properties. We also tabulate crop yield data against production variables using recent field and greenhouse studies. We find evidence to suggest that ADB supplies many more nutrients than PDB and that, in general, biochar can improve nutrient availability indirectly through changes in pH, CEC, soil structure, improved fertiliser efficiency, decreased nutrient leaching and may effect nutrient availability by changing nitrogenous gas release and by changing the soil microbial community, which under some circumstances translates into short term, increased crop yield. Few studies however show complete nutrient, especially N budgets and elaborate on the underlying mechanisms of interaction, especially with regards to microbial induced changes. Also the longevity of the different beneficial effects is questionable as most studies are less than a year long. A synopsis of the literature concludes that biochar application promotes soil water availability, particularly in soils which are degraded or of low quality. Despite this conclusion it is hard to find studies that have adopted methodologies which are fully appropriate to support this notion such as available water capacity and how this changes in response to crop uptake and soil drying. We conclude that the variability in biochar due to variable feedstock and pyrolysis process, as well as particle size and application method, necessitates and also enables production of specific purpose–driven biochars to benefit particular aspects of crop production