THE ECONOMIC SIGNIFICANCE OF CONDITIONING INFORMATION ON PORTFOLIO EFFICIENCY IN THE PRESENCE OF COSTLY SHORT‐SELLING

The economic significance of conditioning information in the presence of costly short‐selling is investigated. Using a compact testing framework, results demonstrate that fixed‐weight stock‐bond portfolios appear inefficient with respect to stock‐bond portfolios with weights determined by extant predictors. However, this result is highly dependent on ex ante knowledge of the predictor set and the ability to short‐sell at low cost. In the absence of such conditions, fixed‐weight stock‐bond portfolios appear efficient with respect to conditioning information.     

On the spatial nature of the groundwater pumping externality

Most existing economic analyses of optimal groundwater management use single-cell aquifer models, which assume that an aquifer responds uniformly and instantly to groundwater pumping. In this paper, we develop an economic model of groundwater management that explicitly incorporates spatial dynamic groundwater flow equations. Calibration of our model to published economic studies of specific aquifers demonstrates that existing studies generally incorrectly estimate the magnitude of the groundwater pumping externality relative to spatially explicit models. In particular, for large aquifers with surface areas of thousands of square miles, the marginal pumping externality predicted by single-cell models may be orders of magnitude less than that predicted by a spatially explicit model, even at large distances from a pumping well. Conversely, for small aquifers with areas of a few hundred square miles or less, single-cell models reasonably approximate the pumping externality. Application of single-cell models to inappropriate settings may result in misleading policy implications due to understatement of the magnitude and spatial nature of the groundwater externality.     

The impact of the use of new technologies on farmers’ wheat yield in Ethiopia: evidence from a randomized control trial

In 2013, Ethiopia's Agricultural Transformation Agency introduced the Wheat Initiative to increase smallholder productivity. In this article, we measure the impacts of the Wheat Initiative package of technologies, and its marketing assistance component alone, on yields among a promotional group of farmers. The package includes improved techniques, improved inputs, and a guaranteed market for the crop. Relying on crop‐cut measures and farmers’ own assessments, we find that full package led to an average 14% higher yields. Implementation of the Wheat Initiative was successful in making certified seed and fertilizer accessible to farmers and increasing their uptake, though only 61% of the intervention group adopted row planting and few farmers received marketing assistance. The measured yield difference may underestimate the true yield difference associated with the technology because of incomplete adoption of the recommended practices by intervention farmers and adoption of some practices by control farmers.     

Does a “Blue Revolution” help the poor? Evidence from Bangladesh

The rapid growth in aquaculture production, globally and in Bangladesh is well documented. Over 2000–2010, per capita production of aquaculture grew 76%, while the consumer price of fish declined 45%. Previous studies have suggested pro‐poor effects of aquaculture based on fish production and consumption patterns. This study attempts to quantify the contribution of aquaculture to income growth and poverty reduction in Bangladesh, using household survey data and a microsimulation approach based on an expanded version of Deaton's concept of net benefit ratio. We estimate that aquaculture's contribution to income growth between 2000 and 2010 was 2.1%, including both price and quantity effects. This income growth was translated into poverty reduction of 1.7 percentage points. Although these estimates seem small, they represent almost 10% of the overall poverty reduction in Bangladesh during the first decade of the 21st century. Put differently, of the 18 million Bengalis who escaped poverty during 2000–2010, about 1.8 million of them managed to do so because of the rapid growth in aquaculture, which contributed to rural income while making fish more accessible to consumers.     

Agriculture,trade openness and emissions: an empirical analysis and policy options

This article investigates the impact of sectoral production allocation, energy usage patterns and trade openness on pollutant emissions in a panel consisting of high‐, medium‐ and low‐income countries. Extended STIRPAT (Stochastic Impact by Regression on Population, Affluence and Technology) and EKC (Environmental Kuznets Curve) models are conducted to systematically identify these factors driving CO2 emissions in these countries during the period 1980–2010. To this end, the study employs three different heterogeneous, dynamic mean group‐type linear panel models and one nonlinear panel data estimation procedure that allows for cross‐sectional dependence. While affluence, nonrenewable energy consumption and energy intensity variables are found to drive pollutant emissions in linear models, population is also found to be a significant driver in the nonlinear model. Both service sector and agricultural value‐added levels play a significant role in reducing pollution levels, whereas industrialisation increases pollution levels. Although the linear model fails to track any significant impact of trade openness, the nonlinear model finds trade liberalisation to significantly affect emission reduction levels. All of these results suggest that economic development, and especially industrialisation strategies and environmental policies, need to be coordinated to play a greater role in emission reduction due to trade liberalisation.     

Real-world cost of treatment for multiple sclerosis patients initiating and receiving infused disease-modifying therapies per recommended label in the United States

Abstract

Aims: The study evaluated the real-world cost of treatment in multiple sclerosis (MS) patients initiating infused disease-modifying-therapies (DMT) in the United States.

Materials and Methods: This retrospective cohort study using administrative claims data included adult patients with MS initiating index infusion DMT (ocrelizumab (OCR), natalizumab (NTZ) or alemtuzumab (ATZ)) from April 2017–September 2018 with 6-months pre/12-months post-index continuous enrollment. The primary cohort included patients who had prescribed annual dosing visits indicated by the approved product label (PL): 3 OCR, 5 ATZ, and 12–13 NTZ infusion visits within the first year of initiation. Annual treatment cost was the sum of all costs on index DMT infusion visit dates. Costs were summarized for a primary and secondary cohort of patients receiving additional doses than prescribed in PL (>3 OCR, >5 ATZ, and >13 NTZ infusion visits); and an overall cohort of patients who met minimum required annual dose (≥3 OCR, ≥5 ATZ, and ≥12 NTZ), further stratified by insurance type.

Results: For patients in the primary cohort (123 OCR, 18 ATZ, and 48 NTZ), mean (standard-deviation) annual cost of treatment with OCR, ATZ, and NTZ cohorts was $72,066 ($34,480), $121,053 ($51,097) and $93,777 ($38,815), respectively. Among patients initiating OCR and NTZ, 15 and 6% respectively, had additional infusion visits leading to greater costs. Mean annual costs of index infusion DMT treatment in the overall cohort (162 patients treated with OCR, 18 with ATZ, 56 with NTZ) were $80,582, $121,053, and $93,807, respectively. The mean costs for commercial enrollees were higher than those for MAPD enrollees.

Limitations: Small sample size, limited population generalizability, and cost-reduction for ATZ beyond the second year need to be accounted for.

Conclusions: Real-world infusion DMT treatment costs for commercially insured patients were higher than perceived expenditures based on wholesale acquisition cost and administration costs via a physician-fee schedule. Consideration of real-world costs in cost-effectiveness and treatment/coverage decisions is needed.     

Convergence to symmetry in dynamic strategic models of R&D: The undiscounted case

Will R&D increase or decrease the asymmetry between firms over time? We examine this issue in the context of a dynamic, alternate-move duopoly model of non-cooperative R&D. The asymmetry we consider is with respect to the initial stocks of technological knowledge which provides one firm a greater potential for current and future profits in the product market. Utilizing a value loss process constructed from the Optimality Equation of dynamic programming, we show that for the undiscounted case the asymmetry between the firms disappears over time. We obtain this convergence-to-symmetry result by imparting a temporal character to R&D through the notion that R&D investment cannot be changed instantaneously, by allowing research externalities, complementarity or substitutability between own and appropriated R&D, and either increasing, decreasing or constant returns to scale in the production of technical knowledge from own and rival R&D.     

Potential Discrimination in Structured Employment Interviews

This experimental study examines the effects of bias toward persons with disabilities (PWDs) upon the employment interview decision process. The design and operationalization of the study permitted examination of the effects of specific disabilities, interview performance, and the resulting interaction between disability and interview performance, using 630 undergraduate students at a major university in the southwestern United States as subjects. The results indicate that (1) interview performance has a favorable, significant main effect upon subsequent HRM decisions, (2) specific disabilities, that is, child care demands, HIV-positive status, and being wheelchair-bound, have unfavorable, significant main effects upon subsequent HRM decisions, and (3) the presence of any of the disabilities decreased the favorable impact of superior interview performance. The limitations of the structured interview to mitigate bias were demonstrated. Given the pervasive, unfavorable treatment directed toward PWDs, it appears that the enactment of the Americans with Disabilities Act of 1990 (1993) is warranted. The public policy implications of these results and recommendations for future research were discussed.     

Unobserved components in an error-correction model of consumption for Southern European countries

In this paper we show how the potential misspecification of the consumption function can be ameliorated by approximating any unmodelled long run variation with an unobserved component in the form of a time-varying trend. This methodology is applied to Greek, Portuguese and Spanish consumption functions during the post-second World war period. The empirical evidence suggests that there are many determinants of long-run consumption in these countries, in addition to income and inflation, and these unobserved long-run effects are captured by a nonstationary stochastic component. The long-run elasticity of consumption with regards to the unobserved component is greater than unity in all countries. First version received: January 1999/Final version received: June 2000