Economic Implications of Alternative Management Strategies for Virginia Oysters and Clams

The Virginia shellfish industry has historically been an important element of the state’s economy. After long-term downward trends in the harvest of wild stocks, clam and oyster production from shellfish aquaculture has been growing. This report provides an analysis of the possible ways to support and enhance this expansion through a variety of shellfish policy options. Three general classes of policy alternatives were considered: 1) state policy to increase private grounds available for shellfish production, 2) state research and development programs, and 3) various financial incentives to increase production. In general, the availability of suitable lease ground is not a large barrier for expansion to oyster aquaculture. Thus, reforms to the state’s current leasing policy are unlikely to stimulate significant new production. Existing clam producers, however, identified ground availability as one of the most significant barriers to increasing production. Unlike existing larger producers, smaller clam growers were more likely to see ground availability as a barrier, providing supporting evidence that clam production would expand if more grounds were made available. In general a slight majority of active shellfish producers surveyed supported opening some of the current (unproductive) Baylor grounds to leased shellfish production. Shellfish aquaculture producers in general identified seed availability and poor water quality as major challenges to the industry. Both oyster and clam producers indicated that state policies to facilitate seed production and improve water quality would do the most to assist their operations. Some conflicts between shellfish growers and surrounding landowners have been widely publicized in the local media, but such conflicts do not appear to be a systematic or widespread obstacle for the industry. Less than 10 percent of oyster growers identified conflicts with surrounding property owners as the most important barrier limiting expansion of their operations. Clam growers expressed even less concern with land owner conflicts. State sponsored shellfish research has the potential to significantly benefit the oyster industry. Over half of all oyster growers indicated that development of triploid oysters and field trials verifying and testing new genetic strands of oysters would be the most useful lines of research. A firm level simulation analysis of oyster aquaculture operations provides additional support for these conclusions. Simulation results suggest that even small increases in oyster growth rates or reductions in oyster mortality can produce relatively large increases in rates of return on investment. Financial (price) incentives can be provided or facilitated by the state in a number of ways including direct and indirect subsidy programs, state supported efforts to enhance market margins (value-added through branding or ecolabeling), or payments for the water quality services provided by oysters. Each activity can potentially increase the effective price growers receive for their product. Based on survey results and economic modeling analysis, if these types of programs could provide relatively small increases in oyster prices then production could increase substantially. For instance a 5 cent increase in price (per oyster) may increase production between 50 and 60 percent. Clam producers may face a more significant offsetting price effect (downward pressure on clam prices) if production were to increase substantially

Acute stroke imaging research roadmap IV : imaging selection and outcomes in acute stroke clinical trials and practice

Background and Purpose: The Stroke Treatment Academic Industry Roundtable (STAIR) sponsored an imaging session and workshop during the Stroke Treatment Academic Industry Roundtable XI via webinar on October 1 to 2, 2020, to develop consensus recommendations, particularly regarding optimal imaging at primary stroke centers. Methods: This forum brought together stroke neurologists, neuroradiologists, neuroimaging research scientists, members of the National Institute of Neurological Disorders and Stroke, industry representatives, and members of the US Food and Drug Administration to discuss imaging priorities in the light of developments in reperfusion therapies, particularly in an extended time window, and reinvigorated interest in brain cytoprotection trials. Results: The imaging session summarized and compared the imaging components of recent acute stroke trials and debated the optimal imaging strategy at primary stroke centers. The imaging workshop developed consensus recommendations for optimizing the acquisition, analysis, and interpretation of computed tomography and magnetic resonance acute stroke imaging, and also recommendations on imaging strategies for primary stroke centers. Conclusions: Recent positive acute stroke clinical trials have extended the treatment window for reperfusion therapies using imaging selection. Achieving rapid and high-quality stroke imaging is therefore critical at both primary and comprehensive stroke centers. Recommendations for enhancing stroke imaging research are provided

HEDONIC PRICE FUNCTIONS: GUIDANCE ON EMPIRICAL SPECIFICATION

The hedonic pricing model is widely accepted as a method for estimating the marginal willingness to pay for spatially delineated amenities. Empirical applications typically rely on one of three functional forms—linear, semi-log, and double-log—and rarely involve rigorous specification testing. This phenomenon is largely due to an influential simulation study by Cropper, Deck and McConnell (CDM) (1988) that found, among other things, that simpler linear specifications outperformed more flexible functional forms in the face of omitted variables. In the 20 years that have elapsed since their study, there have been major computational advances and significant changes in the way hedonic price functions can be estimated. The purpose of our paper is to update and extend the CDM (1988) simulations to investigate current issues in hedonic modeling. Three preliminary results obtained from our theoretically consistent Monte Carlo simulation have been highlighted in this paper: (i) we find that adding spatial fixed effects (census tract dummies) to linear models does improve their performance. This is true both when all attributes are observed, and when some attributes are unobserved, (ii) adding the spatial fixed effects to the more flexible specifications such as the quadratic and quadratic box-cox does not improve their performance when all housing attributes are observed. However, when some housing attributes are unobserved, the spatial fixed effects significantly improves the performance of flexible specifications as well, and (iii) increasing the sample size from CDM’s 200 observations to a sample size of 2000 (which is more representative of modern applications) changes the relative performance of different specifications

Which hedonic models can we trust to recover the marginal willingness to pay for environmental amenities?

The hedonic property value model is among our foremost tools for evaluating the economic consequences of policies that target the supply of local public goods, environmental services, and urban amenities. We design a theoretically consistent and empirically realistic Monte Carlo study of whether omitted variables seriously undermine the method’s ability to accurately identify economic values. Our results suggest that large gains in accuracy can be realized by moving from the standard linear specifications for the price function to a more flexible framework that uses a combination of spatial fixed effects, quasi-experimental identification, and temporal controls for housing market adjustment

HEDONIC PRICE FUNCTIONS: GUIDANCE ON EMPIRICAL SPECIFICATION

The hedonic pricing model is widely accepted as a method for estimating the marginal willingness to pay for spatially delineated amenities. Empirical applications typically rely on one of three functional forms—linear, semi-log, and double-log—and rarely involve rigorous specification testing. This phenomenon is largely due to an influential simulation study by Cropper, Deck and McConnell (CDM) (1988) that found, among other things, that simpler linear specifications outperformed more flexible functional forms in the face of omitted variables. In the 20 years that have elapsed since their study, there have been major computational advances and significant changes in the way hedonic price functions can be estimated. The purpose of our paper is to update and extend the CDM (1988) simulations to investigate current issues in hedonic modeling. Three preliminary results obtained from our theoretically consistent Monte Carlo simulation have been highlighted in this paper: (i) we find that adding spatial fixed effects (census tract dummies) to linear models does improve their performance. This is true both when all attributes are observed, and when some attributes are unobserved, (ii) adding the spatial fixed effects to the more flexible specifications such as the quadratic and quadratic box-cox does not improve their performance when all housing attributes are observed. However, when some housing attributes are unobserved, the spatial fixed effects significantly improves the performance of flexible specifications as well, and (iii) increasing the sample size from CDM’s 200 observations to a sample size of 2000 (which is more representative of modern applications) changes the relative performance of different specifications

Adjusting to natural disasters

People adjust to the risks presented by natural disasters in a number of ways; they can move out of harms way, they can self protect, or they can insure. This paper uses Hurricane Andrew, the largest U.S. natural disaster prior to Katrina, to evaluate how people and housing markets respond to a large disaster. Our analysis combines a unique ex post database on the storm’s damage along with information from the 1990 and 2000 Censuses in Dade County, Florida where the storm hit. The results suggest that the economic capacity of households to adjust explains most of the differences in demographic groups’ patterns of adjustment to the hurricane damage. Low income households respond primarily by moving into low-rent housing in areas that experienced heavy damage. Middle income households move away to avoid risk, and the wealthy, for whom insurance and self-protection are most affordable, appear to remain. This pattern of adjustment with respect to income is roughly mean neutral, so an analysis based on measures of central tendency such as median income would miss these important adjustments. Copyright Springer Science + Business Media, LLC 2006Natural hazards, Economic adjustment, Hurricanes,