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Data Limitations (data + limitation)
Selected AbstractsThe Interplay between Climate Variability and Density Dependence in the Population Viability of Chinook SalmonCONSERVATION BIOLOGY, Issue 1 2006RICHARD W. ZABEL análisis de viabilidad poblacional; especies en peligro; Oncorhynchus tshawytscha Abstract:,The viability of populations is influenced by driving forces such as density dependence and climate variability, but most population viability analyses (PVAs) ignore these factors because of data limitations. Additionally, simplified PVAs produce limited measures of population viability such as annual population growth rate (,) or extinction risk. Here we developed a "mechanistic" PVA of threatened Chinook salmon (Oncorhynchus tshawytscha) in which, based on 40 years of detailed data, we related freshwater recruitment of juveniles to density of spawners, and third-year survival in the ocean to monthly indices of broad-scale ocean and climate conditions. Including climate variability in the model produced important effects: estimated population viability was very sensitive to assumptions of future climate conditions and the autocorrelation contained in the climate signal increased mean population abundance while increasing probability of quasi extinction. Because of the presence of density dependence in the model, however, we could not distinguish among alternative climate scenarios through mean , values, emphasizing the importance of considering multiple measures to elucidate population viability. Our sensitivity analyses demonstrated that the importance of particular parameters varied across models and depended on which viability measure was the response variable. The density-dependent parameter associated with freshwater recruitment was consistently the most important, regardless of viability measure, suggesting that increasing juvenile carrying capacity is important for recovery. Resumen:,La viabilidad de poblaciones esta influida por fuerzas conductoras como la denso dependencia y la variabilidad climática, pero la mayoría de los análisis de viabilidad poblacional (AVP) ignoran estos factores debido a limitaciones en la disponibilidad de datos. Adicionalmente, los AVP simplificados producen medidas limitadas de la viabilidad poblacional tales como la tasa anual de crecimiento poblacional (,) o el riesgo de extinción. Aquí desarrollamos un AVP "mecanicista" de Oncorhynchus tshawytscha en el que, con base en datos detallados de 40 años, relacionamos el reclutamiento de juveniles en agua dulce con la densidad de reproductores, y la supervivencia en el océano al tercer año con índices mensuales de condiciones oceánicas y climáticas a amplia escala. La inclusión de la variabilidad climática en el modelo produjo efectos importantes: la viabilidad poblacional estimada fue muy sensible a las suposiciones de condiciones climáticas futuras y la autocorrelación contenida en la señal climática aumentó la abundancia poblacional promedio al mismo tiempo que incrementó la probabilidad de cuasi extinción. Sin embargo, debido a la presencia de denso densidad en el modelo no pudimos distinguir entre escenarios climáticos alternativos a través de los valores promedio de ,, lo que enfatiza la importancia de considerar medidas múltiples para dilucidar la viabilidad poblacional. Nuestros análisis de sensibilidad demostraron que la importancia de parámetros particulares varió en los modelos y dependió de la medida de viabilidad utilizada como variable de respuesta. El parámetro de denso dependencia asociada con el reclutamiento en agua dulce consistentemente fue el más importante, independientemente de la medida de viabilidad, lo que sugiere que el incremento en la capacidad de carga de juveniles es importante para la recuperación. [source] THE EFFECTS OF FISCAL AND MONETARY DISCIPLINE ON BUDGETARY OUTCOMESCONTEMPORARY ECONOMIC POLICY, Issue 2 2007BILIN NEYAPTI This article extends the model of Von Hagen and Harden that analyzed the impact of fiscal discipline on budgetary outcomes. We modify the model by adding monetary discipline to interact with fiscal discipline in order to analyze the effects of both on budgetary outcomes. The model predicts that while both inflation and budget deficits are negatively associated with fiscal discipline, they may be positively associated with monetary discipline, proxied by central bank independence. This result obtains due to optimizing agents internalizing the burden of spending: inflation. Although not conclusive due to data limitations, empirical findings also support these predictions. (JEL D73, E58, H61, H72) [source] Trends in Parkinson's disease related mortality in England and Wales, 1993,2006EUROPEAN JOURNAL OF NEUROLOGY, Issue 9 2009A. Q. N. Mylne Background:, This paper describes changes in Parkinson's disease (PD) mortality in England and Wales between 1993 and 2006 using all information on death certificates. Methods:, Information on deaths was obtained from the Office for National Statistics. Mortality rates for any mention of PD on death certificates were directly age-standardized using the European standard population. Average yearly changes in mortality rates were estimated using linear regression. The underlying cause of death on death certificates where PD was mentioned was examined by sex and calendar period. Results:, Male PD age-standardized mortality rates for any mention of PD decreased from 15.0 to 11.7 per 100 000 between 1993 and 2006. Female PD mortality rates fell from 6.3 to 4.9 per 100 000. Decreases were greater for older age-groups. The proportion of deaths with PD recorded as the underlying cause increased by 50% in 2001 following implementation of the 10th revision of the International Classification of Diseases (ICD). Conclusion:, Parkinson's disease mortality rates in England and Wales are decreasing, especially for men and for older age-groups. Because of data limitations we are unable to ascertain whether the decrease of PD recorded on death certificates is because of a reduction in PD incidence, or to improved survival for PD patients resulting from advancements in PD treatments or to improvements in general medical care. The dramatic increase in PD as the underlying cause of death following ICD revision in 2001 demonstrates the dangers of using underlying cause of death to investigate mortality trends without being aware of the potential for artifacts. [source] Applying climatically associated species pools to the modelling of compositional change in tropical montane forestsGLOBAL ECOLOGY, Issue 2 2008Duncan J. Golicher ABSTRACT Aim, Predictive species distribution modelling is a useful tool for extracting the maximum amount of information from biological collections and floristic inventories. However, in many tropical regions records are only available from a small number of sites. This can limit the application of predictive modelling, particularly in the case of rare and endangered species. We aim to address this problem by developing a methodology for defining and mapping species pools associated with climatic variables in order to investigate potential species turnover and regional species loss under climate change scenarios combined with anthropogenic disturbance. Location, The study covered an area of 6800 km2 in the highlands of Chiapas, southern Mexico. Methods, We derived climatically associated species pools from floristic inventory data using multivariate analysis combined with spatially explicit discriminant analysis. We then produced predictive maps of the distribution of tree species pools using data derived from 451 inventory plots. After validating the predictive power of potential distributions against an independent historical data set consisting of 3105 botanical collections, we investigated potential changes in the distribution of tree species resulting from forest disturbance and climate change. Results, Two species pools, associated with moist and cool climatic conditions, were identified as being particularly threatened by both climate change and ongoing anthropogenic disturbance. A change in climate consistent with low-emission scenarios of general circulation models was shown to be sufficient to cause major changes in equilibrium forest composition within 50 years. The same species pools were also found to be suffering the fastest current rates of deforestation and internal forest disturbance. Disturbance and deforestation, in combination with climate change, threaten the regional distributions of five tree species listed as endangered by the IUCN. These include the endemic species Magnolia sharpii Miranda and Wimmeria montana Lundell. Eleven vulnerable species and 34 species requiring late successional conditions for their regeneration could also be threatened. Main conclusions, Climatically associated species pools can be derived from floristic inventory data available for tropical regions using methods based on multivariate analysis even when data limitations prevent effective application of individual species modelling. Potential consequences of climate change and anthropogenic disturbance on the species diversity of montane tropical forests in our study region are clearly demonstrated by the method. [source] Application of the distributed hydrology soil vegetation model to Redfish Creek, British Columbia: model evaluation using internal catchment dataHYDROLOGICAL PROCESSES, Issue 2 2003Andrew Whitaker Abstract The Distributed Hydrology Soil Vegetation Model is applied to the Redfish Creek catchment to investigate the suitability of this model for simulation of forested mountainous watersheds in interior British Columbia and other high-latitude and high-altitude areas. On-site meteorological data and GIS information on terrain parameters, forest cover, and soil cover are used to specify model input. A stepwise approach is taken in calibrating the model, in which snow accumulation and melt parameters for clear-cut and forested areas were optimized independent of runoff production parameters. The calibrated model performs well in reproducing year-to-year variability in the outflow hydrograph, including peak flows. In the subsequent model performance evaluation for simulation of catchment processes, emphasis is put on elevation and temporal differences in snow accumulation and melt, spatial patterns of snowline retreat, water table depth, and internal runoff generation, using internal catchment data as much as possible. Although the overall model performance based on these criteria is found to be good, some issues regarding the simulation of internal catchment processes remain. These issues are related to the distribution of meteorological variables over the catchment and a lack of information on spatial variability in soil properties and soil saturation patterns. Present data limitations for testing internal model accuracy serve to guide future data collection at Redfish Creek. This study also illustrates the challenges that need to be overcome before distributed physically based hydrologic models can be used for simulating catchments with fewer data resources. Copyright © 2003 John Wiley & Sons, Ltd. [source] What Small Spatial Scales Are Relevant as Electoral Contexts for Individual Voters?AMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 3 2009The Importance of the Household on Turnout at the 2001 General Election For many years, scholars of voting behavior have been thwarted in their attempts to identify micro spatial variations in turnout by data limitations. This has meant that most analyses have been ecological, which has implications for valid inference. Here, for the first time, a hierarchical approach is used to show the relative importance of several micro spatial scales, including the household, on voter participation. The findings highlight the importance of the household context. While those who live together often turn out together, the relative level of clustering within households as opposed to between geographical areas is found to be more important for two-person households compared to other households. Even after taking account of whether individuals are likely to self-select others from similar social backgrounds or with similar political attitudes, there is strong evidence of large and significant household effects on voter participation. [source] On the Specification and Estimation of the Production Function for Cognitive Achievement*THE ECONOMIC JOURNAL, Issue 485 2003Petra E. Todd This paper considers methods for modelling the production function for cognitive achievement in a way that captures theoretical notions that child development is a cumulative process depending on the history of family and school inputs and on innate ability. It develops a general modelling framework that accommodates many of the estimating equations used in the literatures. It considers different ways of addressing data limitations, and it makes precise the identifying assumptions needed to justify alternative approaches. Commonly used specifications are shown to place restrictive assumptions on the production technology. Ways of testing modelling assumptions and of relaxing them are discussed. [source] Who Are the Potential Smokers of Smuggled Cigarettes?ASIAN ECONOMIC JOURNAL, Issue 3 2010Hsin-Fan Chen I18; C25 Although smuggled cigarettes have been a prevalent problem and a severe challenge to public health and welfare around the world, little is known about the behavior associated with smoking smuggled cigarettes and the issue is difficult to study due to data limitations. By means of a population-based tobacco survey conducted in Taiwan, the present paper applies a latent class model to identify potential smokers who are either currently or will at some point in the future be consuming smuggled cigarettes. This methodology, in contrast to the traditional discrete models, allows potential smokers who are more inclined to smoke smuggled cigarettes to be endogenously classified. The empirical results indicate that socio-demographic factors do increase the inclination to smoke smuggled cigarettes after unobserved heterogeneity has been accounted for. [source] Growth with or without Equity?ASIAN-PACIFIC ECONOMIC LITERATURE, Issue 2 2002The distributional impact of Indonesian development This paper surveys articles that have examined and sought to explain the distributional change experienced in Indonesia during the past 30 years of rapid economic development. The literature is critically evaluated, and methodological difficulties and current data limitations are highlighted and point the way for advances in future research. [source] Neonatal Mortality for Primary Cesarean and Vaginal Births to Low-Risk Women: Application of an "Intention-to-Treat" ModelBIRTH, Issue 1 2008Marian F. MacDorman PhD ABSTRACT: Background: The percentage of United States births delivered by cesarean section continues to increase, even for women considered to be at low risk for the procedure. The purpose of this study was to use an "intention-to-treat" methodology, as recommended by a National Institutes of Health conference, to examine neonatal mortality risk by method of delivery for low-risk women. Methods: Low-risk births were singleton, term (37,41 weeks' gestation), vertex births, with no reported medical risk factors or placenta previa and with no prior cesarean section. All U.S. live births and infant deaths for the 1999 to 2002 birth cohorts (8,026,415 births and 17,412 infant deaths) were examined. Using the intention-to-treat methodology, a "planned vaginal delivery" category was formed by combining vaginal births and cesareans with labor complications or procedures since the original intention in both cases was presumably a vaginal delivery. This group was compared with cesareans with no labor complications or procedures, which is the closest approximation to a "planned cesarean delivery" category possible, given data limitations. Multivariable logistic regression was used to model neonatal mortality as a function of delivery method, adjusting for sociodemographic and medical risk factors. Results: The unadjusted neonatal mortality rate for cesarean deliveries with no labor complications or procedures was 2.4 times that for planned vaginal deliveries. In the most conservative model, the adjusted odds ratio for neonatal mortality was 1.69 (95% CI 1.35,2.11) for cesareans with no labor complications or procedures, compared with planned vaginal deliveries. Conclusions: The finding that cesarean deliveries with no labor complications or procedures remained at a 69 percent higher risk of neonatal mortality than planned vaginal deliveries is important, given the rapid increase in the number of primary cesarean deliveries without a reported medical indication. (BIRTH 35:1 March 2008) [source] | ||||||||||||||||