Productivity Estimates (productivity + estimate)

Distribution by Scientific Domains

Selected Abstracts

Bias from Farmer Self-Selection in Genetically Modified Crop Productivity Estimates: Evidence from Indian Data

Benjamin Crost
Q12; D81 Abstract In the continuing debate over the impact of genetically modified (GM) crops on farmers of developing countries, it is important to accurately measure magnitudes such as farm-level yield gains from GM crop adoption. Yet most farm-level studies in the literature do not control for farmer self-selection, a potentially important source of bias in such estimates. We use farm-level panel data from Indian cotton farmers to investigate the yield effect of GM insect-resistant cotton. We explicitly take into account the fact that the choice of crop variety is an endogenous variable which might lead to bias from self-selection. A production function is estimated using a fixed-effects model to control for selection bias. Our results show that efficient farmers adopt Bacillus thuringiensis (Bt) cotton at a higher rate than their less efficient peers. This suggests that cross-sectional estimates of the yield effect of Bt cotton, which do not control for self-selection effects, are likely to be biased upwards. However, after controlling for selection bias, we still find that there is a significant positive yield effect from adoption of Bt cotton that more than offsets the additional cost of Bt seed. [source]

Economic evaluation of surgically trained assistant medical officers in performing major obstetric surgery in Mozambique

ME Kruk
Objective, To compare the training and deployment costs and surgical productivity of surgically trained assistant medical officers (técnicos de cirurgia) and specialist physicians (surgeons and obstetrician/gynaecologists) in Mozambique in order to inform health human resource planning in a developing country with low availability of obstetric care and severe physician shortages. Técnicos de cirurgia have been previously shown to have quality of care outcomes comparable to physicians. Design, Economic evaluation of costs and productivity of surgically trained assistant medical officers and specialist physicians. Setting, Hospitals and health science training institutions in Mozambique. Population, Surgically trained assistants, medical officers, surgeons and obstetrician/gynaecologists in Mozambique. Methods, The costs of training and deploying the two cadres of health workers were derived from a review of budgets, annual expenditure reports, enrolment registers, and accounting statements from training institutions and interviews with directors and administrators. Productivity estimates were based on a hospital survey of physicians and técnicos de cirurgia. Main outcome measures, Cost per major obstetric surgical procedure over 30 years in 2006 US dollars. Results, The 30-year cost per major obstetric surgery was $38.9 for técnicos de cirurgia and $144.1 for surgeons and obstetrician/gynaecologists. Doubling the salaries of técnicos de cirurgia resulted in a smaller but still substantial difference in cost per surgery between the groups ($60.3 versus $144.1 per procedure). One-way sensitivity analysis to test the impact of varying other inputs did not substantially change the magnitude of the cost advantage of técnicos de cirurgia. Conclusion, Training more mid-level health workers in surgery can be part of the response to the health worker shortage, which today threatens the achievement of the health Millennium Development Goals in developing countries. [source]

16 Comparisons of macrophyte cover and community primary productivity on two southern california shores

A. M. Bullard
Light-saturated net photosynthetic rates and cover of rocky intertidal macrophytes were determined between January and March 2003 at two southern California sites characterized by different macrophyte standing stocks. Overall macrophyte cover at Little Corona del Mar was low (75.4%) and was dominated by articulated corallines, and small, turf-forming crustose algae that provide little habitat structure. Macrophyte cover was higher at Dana Point (99.4%), where larger, frondose seaweeds were more abundant (34% vs < 5% cover). Our light-saturated photosynthetic rates for Little Corona del Mar and Dana Point macrophytes were similar to values for the same species obtained during the 1970s and 1980s. Highest photosynthetic rates were obtained for thinner, sheet-like, and branched, frondose seaweeds, while lowest rates were found for articulated coralline and crustose algae. We estimated the net community productivity of the two sites using photosynthetic rates (calculated as mg C m,2 · h,1) and percent cover data for the most abundant populations. We also compared our community productivity estimates for Little Corona del Mar and Dana Point with values for the same sites calculated using macrophyte cover values obtained during the mid-1970s. Re-sampling studies of these and other regional sites reveal that lower-producing, crustose and coralline algae have become increasingly abundant while the cover of higher-producing, frondose algae has declined on many southern California shores. Our studies at Little Corona del Mar and Dana Point, indicate that changing macrophyte abundances can have significant effects on the primary productivity of rocky intertidal communities. [source]

55 Ice age kelp forests: climate-driven changes in kelp forest distribution since the last glacial maximum

M. H. Graham
Kelp forest distributions are constrained by the availability of rocky substrate within the depth range tolerable for growth and reproduction, which can vary over relatively short geological timescales (millennia) due to interactions between coastal bathymetry and climate-driven changes in eustatic sea level. Using GIS, a digital bathymetric map, sea level curves, and published kelp depth tolerances, I reconstructed changes in the size and distribution of giant kelp (Macrocystis pyrifera) forests in the Southern California Bight since the last glacial maximum. Reconstructions predicted that the total area of available kelp forest habitat for the California Channel Islands during the last glacial maximum (18.5 kyr BP; 628 square km) was greater than at present (382 square km) but less than at 16.5 kyr BP (1130 square km). Available kelp forest habitat along the southern California mainland also increased rapidly from 18.5 to 16.5 kyr BP but continued to increase with sea level rise. Differences in the effects of sea level rise on coastal geomorphology between the islands and mainland further constrained the extent of rocky substrate available to kelps. Given biomass and productivity estimates from present-day kelp forests, these reconstructions suggest more productive and spatially extensive island kelp forests near the last glacial maximum than at present, but the opposite pattern for the mainland. These climate-driven changes in kelp forest distribution and productivity likely had important historical impacts on the ecology and evolution of the present-day kelp ecosystem including kelp forest exploitation by early human inhabitants of southern California. [source]

Farm-level efficiency and productivity measurement using panel data: wool production in south-west Victoria

Iain Fraser
In this article we explore some issues surrounding the use of farm-level efficiency and productivity estimates for benchmarking studies. Using an eight-year balanced panel of Victorian wool producers we analyse annual variation between estimates of farm-level technical efficiency derived using Data Envelopment Analysis and Malmquist estimates of Total Factor Productivity. We find that farms change their relative rank in terms of efficiency across years. Also, unlike aggregate studies of Total Factor Productivity, we find at best erratic and modest growth, a worrying result for this industry. However, caution is needed when interpreting these results, and for that matter, benchmarking analysis as currently practised when using frontier estimation techniques like Data Envelopment Analysis. [source]