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961.
This paper studies determinants of income inequality using a newly assembled panel of 16 countries over the entire twentieth century. We focus on three groups of income earners: the rich (P99–100), the upper middle class (P90–99), and the rest of the population (P0–90). The results show that periods of high economic growth disproportionately increases the top percentile income share at the expense of the rest of the top decile. Financial development is also pro-rich and the outbreak of banking crises is associated with reduced income shares of the rich. Trade openness has no clear distributional impact (if anything openness reduces top shares). Government spending, however, is negative for the upper middle class and positive for the nine lowest deciles but does not seem to affect the rich. Finally, tax progressivity reduces top income shares and when accounting for real dynamic effects the impact can be important over time.  相似文献   
962.
  总被引:1,自引:0,他引:1  
\"This paper introduces general methods for quantitative analysis of the role of population in environmental change. The approach is applicable over a wide range of environmental issues, and arbitrary regions and time periods. First, a single region is considered, appropriate formulae derived, and the limitations to quantitative approaches discussed. The approach is contrasted to earlier formulations, and shown to avoid weaknesses in a common approximation. Next, the analysis is extended to the multiple region problem. An apparent paradox in aggregating regional estimates is illuminated, and the risk of misleading results is underscored. The methods are applied to the problem of climate change with two case studies, an historical period and a future scenario, used to illustrate the results. The contribution of change in population to change in green house gas emissions is shown to be significant, but not dominant in both industrialized and developing regions.\"  相似文献   
963.
964.
The U.S. Departments of Agriculture and Energyjointly analyzed the economic potential for,and impacts of, large-scale bioenergy cropproduction in the United States. Anagricultural sector model (POLYSYS) wasmodified to include three potential bioenergycrops (switchgrass, hybrid poplar, and willow). At farmgate prices of US $2.44/GJ, anestimated 17 million hectares of bioenergycrops, annually yielding 171 million dry Mg ofbiomass, could potentially be produced at aprofit greater than existing agricultural usesfor the land. The estimate assumes highproductivity management practices are permittedon Conservation Reserve Program lands. Traditional crops prices are estimated toincrease 9 to 14 percent above baseline pricesand farm income increases annually by US $6.0billion above baseline.At farmgate prices of US $1.83/GJ, anestimated 7.9 million hectares of bioenergycrops, annually yielding 55 million dry Mg ofbiomass, could potentially be produced at aprofit greater than existing agricultural usesfor the land. The estimate assumes managementpractices intended to achieve highenvironmental benefits on Conservation ReserveProgram lands. Traditional crops prices areestimated to increase 4 to 9 percent abovebaseline prices and farm income increasesannually by US $2.8 billion above baseline.  相似文献   
965.
966.
Continental breakup, or compressive lithosphere scale faulting, requires a physical mechanism for wholesale faulting of the lithosphere. We compared numerical and experimental models for the nucleation of quasi-adiabatic shear bands in polyvinylchloride (PVC) with those in an idealized viscoelastoplastic mantle with olivine rheology. In both materials fault nucleation is caused by elastic stress concentration on pre-existing imperfections, with localized yielding confined to its vicinity. Faulting occurs rapidly after the initial elastic energy in the system is charged sufficiently to cause wholesale yielding. Propagation of the fault, monitored by looking at the dissipation of plastic energy, reveals migration of a sharp, thermal-mechanical “crack”- like instability, which appears in the temperature field as a slightly diffused signal. The initial temperature rise in the crack is subtle but increases suddenly when the plate is severed. This autocatalytic behavior has also been described in ductile polymers, which can be used as mechanical analogues. We suggest that elastoplastic coupling in quasi-adiabatic shear banding is a key for fast (< 1 Ma) nucleation of shear zones. These nonlinear phenomena will be illustrated for both experimental and numerical results by nine movies  相似文献   
967.
968.
Summary. Bick (1987,1990) and He and Leland (1993) demonstrated that not every arbitrage-free Markovian diffusion price process is consistent with an equilibrium approach. We propose a unified framework for these results and we derive a new martingale characterization of equilibrium.  相似文献   
969.
    
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970.
    
Agriculture remains sensitive to variation in rainfall and temperature. Fortunately, our ability to predict the lower frequency variation in the earth's atmosphere is increasing rapidly. While information cannot affect the underlying source of variability, it allows unexpected shocks to be anticipated and acted upon. This paper develops and analyzes an intertemporal Ricardian trade model with Bayesian beliefs. Results in this paper show that improved climate prediction reduces expected prices, but increases price variability. In addition, trade is crucial to realizing the potential benefits of climate prediction. The value of climate prediction is highest with both storage and trade, and falls by over 300% when a country is in autarky.  相似文献   
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