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Accurate estimates of mortality at advanced ages are essential to improving forecasts of mortality and the population size of the oldest old age group. However, estimation of hazard rates at extremely old ages poses serious challenges to researchers: (1) The observed mortality deceleration may be at least partially an artifact of mixing different birth cohorts with different mortality (heterogeneity effect); (2) standard assumptions of hazard rate estimates may be invalid when risk of death is extremely high at old ages and (3) ages of very old people may be exaggerated. One way of obtaining estimates of mortality at extreme ages is to pool together international records of persons surviving to extreme ages with subsequent efforts of strict age validation. This approach helps researchers to resolve the third of the above-mentioned problems but does not resolve the first two problems because of inevitable data heterogeneity when data for people belonging to different birth cohorts and countries are pooled together. In this paper we propose an alternative approach, which gives an opportunity to resolve the first two problems by compiling data for more homogeneous single-year birth cohorts with hazard rates measured at narrow (monthly) age intervals. Possible ways of resolving the third problem of hazard rate estimation are elaborated. This approach is based on data from the Social Security Administration Death Master File (DMF). Some birth cohorts covered by DMF could be studied by the method of extinct generations. Availability of month of birth and month of death information provides a unique opportunity to obtain hazard rate estimates for every month of age. Study of several single-year extinct birth cohorts shows that mortality trajectory at advanced ages follows the Gompertz law up to the ages 102-105 years without a noticeable deceleration. Earlier reports of mortality deceleration (deviation of mortality from the Gompertz law) at ages below 100 appear to be artifacts of mixing together several birth cohorts with different mortality levels and using cross-sectional instead of cohort data. Age exaggeration and crude assumptions applied to mortality estimates at advanced ages may also contribute to mortality underestimation at very advanced ages. 相似文献
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Two distinctive regimes are distinguished in Spain over half a millennium. The first one (1270s–1590s) corresponds to a high land–labour ratio frontier economy, which is pastoral, trade‐oriented, and led by towns. Wages and food consumption were relatively high. Sustained per capita growth occurred from the end of the Reconquest (1264) to the Black Death (1340s) and resumed from the 1390s only broken by late fifteenth‐century turmoil. A second regime (1600s–1810s) corresponds to a more agricultural and densely populated low‐wage economy which, although it grew at a pace similar to that of 1270–1600, remained at a lower level. Contrary to pre‐industrial western Europe, Spain achieved its highest living standards in the 1340s, not by mid‐fifteenth century. Although its death toll was lower, the plague had a more damaging impact on Spain and, far from releasing non‐existent demographic pressure, destroyed the equilibrium between scarce population and abundant resources. Pre‐1350 per capita income was reached by the late sixteenth century but only exceeded after 1820. 相似文献
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This paper presents Uganda's experience with aid flows overthe period 1970-96. It discusses the compilation of aid dataand also reviews the chronological developments in aid flowsto Uganda. Over this period, the sectoral distribution and typeof aid is largely dictated by the government's economic programmesin place. The period 1962-71 largely reflects government borrowingfor on-lending to agriculture and industry whereas the period1979-85 shows a wider range of sector-specific programmes drivenby the need to reconstruct and rehabilitate the economy. Althoughthe need to reconstruct and rehabilitate the economy continued,support for policy reform began to take up an increasing proportionof aid over the period 1987-96. We also analyse the impact ofaid on some major macroeconomic variables and find that investmentand real exchange rate developments have been largely drivenby official development aid flows. Although we find a similarrelationship between aid and improved policy environment, thefindings show that in the latter part, i.e., 1992-6, the continuedpolicy reform was driven more by ownership of the programmethan by aid. Indeed, in this latter period, the aid/GDP ratiosdeclined. The major lesson drawn from this study is that ownershipof a reform programme is more critical for its success, henceour conclusion that aid should be used for financing ratherthan buying reforms. 相似文献
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新时期西部农村反贫困,对于推进城乡统筹、和谐社会以及社会主义新农村建设具有特殊的重大战略意义。对大量的调查数据资料分析表明,新时期西部农村贫困除了人口数量大分布广之外,还呈现贫困程度深、边境性、民族性与脆弱生态环境空间分布高度一致性等新的特征。西部地区城乡统筹必须将农村反贫困问题纳入其要义之中。 相似文献
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Leonid A. Gavrilov PhD Natalia S. Gavrilova PhD 《North American actuarial journal : NAAJ》2013,17(3):432-447
Abstract Accurate estimates of mortality at advanced ages are essential to improving forecasts of mortality and the population size of the oldest old age group. However, estimation of hazard rates at extremely old ages poses serious challenges to researchers: (1) The observed mortality deceleration may be at least partially an artifact of mixing different birth cohorts with different mortality (heterogeneity effect); (2) standard assumptions of hazard rate estimates may be invalid when risk of death is extremely high at old ages and (3) ages of very old people may be exaggerated. One way of obtaining estimates of mortality at extreme ages is to pool together international records of persons surviving to extreme ages with subsequent efforts of strict age validation. This approach helps researchers to resolve the third of the above-mentioned problems but does not resolve the first two problems because of inevitable data heterogeneity when data for people belonging to different birth cohorts and countries are pooled together. In this paper we propose an alternative approach, which gives an opportunity to resolve the first two problems by compiling data for more homogeneous single-year birth cohorts with hazard rates measured at narrow (monthly) age intervals. Possible ways of resolving the third problem of hazard rate estimation are elaborated. This approach is based on data from the Social Security Administration Death Master File (DMF). Some birth cohorts covered by DMF could be studied by the method of extinct generations. Availability of month of birth and month of death information provides a unique opportunity to obtain hazard rate estimates for every month of age. Study of several single-year extinct birth cohorts shows that mortality trajectory at advanced ages follows the Gompertz law up to the ages 102–105 years without a noticeable deceleration. Earlier reports of mortality deceleration (deviation of mortality from the Gompertz law) at ages below 100 appear to be artifacts of mixing together several birth cohorts with different mortality levels and using cross-sectional instead of cohort data. Age exaggeration and crude assumptions applied to mortality estimates at advanced ages may also contribute to mortality underestimation at very advanced ages. 相似文献
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THE EFFICIENCY OF SEQUESTERING CARBON IN AGRICULTURAL SOILS 总被引:2,自引:0,他引:2
Agricultural tillage practices are important human-induced activities that can alter carbon emissions from agricultural soils and have the potential to contribute significantly to reductions in greenhouse gas emission (Lal et al., The Potential of U.S. Cropland, 1998). This research investigates the expected costs of sequestering carbon in agricultural soils under different subsidy and market-based policies. Using detailed National Resources Inventory data, we estimate the probability that farmers adopt conservation tillage practices based on a variety of exogenous characteristics and profit from conventional practices. These estimates are used with physical models of carbon sequestration to estimate the subsidy costs of achieving increased carbon sequestration with alternative subsidy schemes. 相似文献