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Since the 1990s, the issue of regional income convergence and its long‐term tendencies has been thoroughly and heatedly discussed. Much less attention, however, has been devoted to the short‐run dynamics of regional convergence. In particular, three important aspects have not yet been adequately addressed. First, it is indeed essential to understand whether regional disparities manifest a tendency to move systematically along the national cycle. Then, if this happens to be the case, it becomes crucial to know whether 1) these movements are pro‐ or counter‐cyclical,2) the cyclical evolution of the disparities is a consequence of differences in the timing with which the business cycle is felt in regions or it is motivated by the amplitude differences across local cyclical swings. In this paper, we shed light on these issues using data on personal income for the 48 coterminous U.S. states between 1969 and 2008. Our results indicate that income disparities do not move randomly in the short run but follow a distinct cyclical pattern, moving either pro‐ or counter‐cyclically depending on the period of analysis. These patterns are probably explained by the changes in the direction of capital and labor flows that favor developed or poorer states in different periods. As for the underlying mechanism, it appears that the short‐run evolution of the disparities in recent years is largely a consequence of differences in the timing with which the business cycle is felt across states rather than the outcome of amplitude differences across local cyclical swings.  相似文献   

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In the southern United States, corn production encounters moisture deficit coupled with high‐temperature stress, particularly during the reproductive stage of the plant. In evaluating plants for environmental stress tolerance, it is important to monitor changes in their physical environment under natural conditions, especially when there are multiple stress factors, and integrate this information with their physiological responses. A low‐cost microcontroller‐based monitoring system was developed to automate measurement of canopy, soil and air temperatures, and soil moisture status in field plots. The purpose of this study was to examine how this system, in combination with physiological measurements, could assist in detecting differences among corn genotypes in response to moisture deficit and heat stress. Three commercial hybrids and two inbred germplasm lines were grown in the field under irrigated and non‐irrigated conditions. Leaf water potential, photosynthetic pigments, cell membrane thermostability (CMT) and maximum quantum efficiency of photosystem II (Fv/Fm) were determined on these genotypes under field and greenhouse conditions. Variations observed in air and soil temperatures, and soil moisture in plots of the individual corn genotypes helped explain their differences in canopy temperature (CT), and these variations were reflected in the physiological responses. One of the commercial hybrids, having the lowest CT and the highest CMT, was the most tolerant among the genotypes under moisture deficit and heat stress conditions. These results demonstrated that the low‐cost microcontroller‐based monitoring system, in combination with physiological measurements, was effective in evaluating corn genotypes for drought and heat stress tolerance.  相似文献   

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ABSTRACT This paper examines how the college‐educated population—segmented into selective demographic groups, from young adults to the elderly—differentially values quality‐of‐life (QOL) indicators of metropolitan areas in the United States. Using data from the 2000 Census and the 1997 Places Rated Almanac, out‐migration patterns are shown to depend jointly upon stage in the life course, the spatial‐demographic setting, and QOL characteristics. An abundance of cultural and recreational amenities lowers out‐migration rates of young college‐educated. For the older college‐educated population, the revealed preferences shift toward concerns for safety and a strong preference for milder climates. The study also finds significantly lower out‐migration rates for metropolitan areas with growing human capital. In light of shifting age distributions and rising educational attainment levels, the results have important implications for the emergence of new migration patterns and the concentration of human capital.  相似文献   

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In the low‐rainfall region of south‐eastern Australia, distinctive soil types reflecting the typical landscape of higher elevated dunes and swale zones at the bottom can be found within one field. Different soil characteristics cause consequently large variability in cropping productivity between soils and across seasons. To assess the possibilities for zone‐specific management, five farmer fields were zoned into a dune, mid‐slope and swale zone. For each site, zone yields were mapped over 2 years and soil properties were surveyed. This information was used to parameterize and validate the APSIM model for each zone. Field‐measured PAWC increased from the dune to the swale zone. On‐farm results and simulation analysis showed distinctive yield performance of the three designed zones. However, yield is not related to PAWC, it is rather a complex relationship between soil type, fertility and rainfall. While in high‐rainfall years, the swale zones yielded higher due to higher soil organic carbon content and less drainage losses, the dune zones performed better in the low‐rainfall years due to lower evaporation losses. This study emphasizes that in this specific environment where soil variation in texture and subsoil constraints strongly influence crop performance, mechanistic crop models and long‐term field observations are necessary for better understanding of zone‐specific performance, and simple linear relationships across years or sites are not useful.  相似文献   

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This paper analyses the major determinants of long‐ and short‐run labour productivity evolution for Chinese provinces between 1978 and 2010. The role played by openness to trade and foreign direct investment (FDI) constitutes the main focus of this analysis. From a methodological perspective, our main contribution is the inclusion of spatial effects into a dynamic error correction modelling framework. The results show that, in addition to domestic factors such as investment intensity and infrastructure use, trade openness and inward FDI also exert a direct impact on labour productivity. Furthermore, the geographical environment has a strong indirect influence on productivity: The more a region is surrounded by high‐productive regions with good infrastructure and linkages to the world economy, the higher are its productivity level and growth rate. The magnitude of these impacts varies by spatial regime (coastal, interior provinces) and time period in focus. Especially in the recent past, trade and FDI activity appear to be increasingly important drivers of regional productivity evolution, both for coastal and interior regions. These findings have important policy implications: In order to fully exploit the benefits from such spillovers, coordinated industrial policies which foster regional complementarities and support the free movement of production factors across regional borders are crucial.  相似文献   

8.
Climate change has become a global issue influencing human survival and development while low‐carbon is the inevitable choice. As the world’s largest emitter of greenhouse gases, China has become an important force that influences the cooperation of climate change. China is a large agricultural country, and the rural carbon emissions have been gradually increasing. We consider rural neighborhood as an important space for the use of low‐carbon ideas to address climate change. There is no specific assessment system for a rural neighborhood. The studies of rural neighborhood low‐carbon mainly focus on the method of calculation carbon emissions. However, only quantifying rural carbon emissions is insufficient. In this paper, a low‐carbon evaluation indicator system has been proposed for rural neighborhood and Fuzzy Comprehensive Evaluation has been applied to get the low‐carbon degree. Considering the influence and feedback inside the indicator system, Analytic Network Process was applied to get the weights. Furthermore, a case study was carried out for the using of the proposed method in an eco‐village of China. Our practice has proved that the system is easy to operate in rural neighborhood.  相似文献   

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This paper aims to construct a comprehensive model capable of simulating spatial unemployment disparities. The key feature of the model is that it simultaneously deals with commuting and migration. Much of the existing literature simply models one adjustment mechanism at a time. This paper adopts a micro‐simulation approach to build a model which can deal with equilibrium and disequilibrium unemployment disparities in a context where commuting and migration are possible. The model is then used to demonstrate the importance of considering both types of flows and to guide future empirical and theoretical work in the area.  相似文献   

10.
转基因抗草甘膦抗虫棉田害虫群落多样性季节动态研究   总被引:2,自引:0,他引:2  
为了明确转基因抗草甘膦抗虫棉对棉田害虫群落多样性的影响,于2010-2012年,在田间隔离条件下,采用直接观察法,分析比较多样性指数、优势集中性指数、均匀性指数、优势种和优势度等相关参数。结果表明,在6月中下旬及7月中下旬至8月上旬,转基因抗草甘膦抗虫棉田害虫群落多样性指数和均匀性指数显著高于常规棉,而其优势集中性显著低于常规棉;与Bt棉相比,二者在同时期的害虫群落参数变化趋势基本一致,差异不明显。3种棉田在其他时段的群落参数变化趋势一致,无明显差异。同时,转基因抗草甘膦抗虫棉田的优势害虫种类比较稳定;因此,种植该双抗棉对棉田害虫群落结构的影响较小,不会扰乱害虫群落的稳定性。  相似文献   

11.
In this paper we examine how internal migration redistributes earned income across U.S. states between 1995 and 2010. We examine interregional income flows by first describing the movement of earned income between U.S. states. Second, we examine the effect of income migration on spatial patterns of income inequality. The question we ask is, “does migration increase or decrease convergence income across U.S. States?” A primary contribution of this paper is that instead of using only 1 year of income migration data to explore these issues, we use yearly data from the first year the Internal Revenue Service (IRS) data started including income (1995/1996) up to the most current data available (2009/2010). Results indicate that income convergence/divergence across states varies by whether or not there is general economic expansion or contraction. Nevertheless, some high‐amenity states continually attract high‐income households.  相似文献   

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广州市叶菜田杂草群落组成及其年动态变化   总被引:2,自引:2,他引:0  
于2008年利用倒置“W”九点取样法对广州市叶菜田杂草群落年动态变化进行了调查。调查共计发现60种杂草,属23科,45属。春季杂草群落为马齿苋(Portulaca oleracea)+繁缕(stellaria media)+腋花蓼(Echinochloa colonum)为主;夏季以马齿苋+碎米莎草(Cyperus iria)+凹头苋(Amaranthus lividus)为主;秋季以马齿苋+凹头苋+光头稗(Echinochloa colonum)为主;冬季以腋花蓼+繁缕+酸模叶蓼(Polygonum lapathifolium)为主。通过计算杂草的优势度得出全年危害最严重的杂草为马齿苋、繁缕、腋花蓼、酸模叶蓼、凹头苋、碎米莎草、马唐(Digitaria sanguinalis)、牛筋草(Eleusine indica)、光头稗、小藜(Cardamine hirsuta)等10种。其中,马齿苋、凹头苋、碎米莎草在春夏秋季为优势杂草;马唐在夏秋冬为优势杂草;光头稗、牛筋草为春秋季优势杂草;繁缕、腋花蓼、酸模叶蓼、小藜为冬春季优势杂草。  相似文献   

14.
Based on an extensive literature review on intelligent cities, smart cities, and happy cities, and on their conceptual connections with citizens' well‐being, quality of life, and happiness, we developed a resource‐based view on City Quality: the PESNAT (political, economic, social, natural, artificial, and technological) framework. The concept of City Quality rests on the idea of cities interconnected sub‐habitats—PESNAT—which are powerful analytical categories needed for understanding cities as complex and intricate loci. This framework eventually aims at assessing the cities' power to attract businesses and people, to contribute to a sustainable development of the city and an increased quality of life. Furthermore, two hypotheses are outlined regarding the level of importance of each sub‐habitat in relation to happiness, and the level of controversy of each one for citizens, city planners, and decision makers.  相似文献   

15.
ABSTRACT This article integrates firm birth and death data into a shift‐share analysis framework. The proposed methodology can be used when data availability does not allow for the direct association of employment changes to business demographics at the regional level. It may be also used as an exploratory step before any explanatory econometric work is undertaken as a means of identifying classes of potential control variables. Applying the method to Greek data suggests that firm‐size heterogeneity should not be ignored, that local conditions matter more than regional economic structure, and that the latter are asymmetrical across sectors when it comes to the effects of business demographics on regional employment or output growth.  相似文献   

16.
Breeding sorghum for low‐input conditions is hindered by soil heterogeneity. Spatial adjustment using mixed models can help account for this variation and increase precision of low‐input field trials. Large small‐scale spatial variation (CV 39.4 %) for plant available phosphorus was mapped in an intensely sampled low‐input field. Spatial adjustments were shown to account for residual yield differences because of this and other growth factors. To investigate the potential of such models to increase the efficiency of low‐ and high‐input field trials, 17 experiments with 70 sorghum genotypes conducted in Mali, West Africa, were analysed for grain yield using different mixed models including models with autoregressive spatial correlation terms. Spatial models (AR1, AR2) improved broad sense heritability estimates for grain yield, averaging gains of 10 and 6 % points relative to randomized complete block (RCB) and lattice models, respectively. The heritability estimate gains were even higher under low phosphorus conditions and in two‐replicate analyses. No specific model was best for all environments. A single spatial model, AR1 × AR1, captured most of the gains for heritability and relative efficiency provided by the best model identified for each environment using Akaike's Information Criterion. Spatial modelling resulted in important changes in genotype ranking for grain yield. Thus, the use of spatial models was shown to have potentially important consequences for aiding effective sorghum selection in West Africa, particularly under low‐input conditions and for trials with fewer replications. Thus, using spatial models can improve the resource allocation of a breeding program. Furthermore, our results show that good experimental design with optimal placement and orientation of blocks is essential for efficient statistical analysis with or without spatial adjustment.  相似文献   

17.
Many researchers and practitioners agree that evaluation of economic development planning programs is important, although the perspectives on the approaches, methods, and use of results vary widely. Confounding the issue are cases in which development programs have a small number of participants and typical measures such as parametric statistics are not valid. The alternate evaluation technique presented here uses a non‐parametric approach, incorporating a control group for comparison purposes. The paper begins with a review of evaluation issues for economic development planning programs, followed by an illustration of the approach suitable for programs with small numbers of participants. It utilizes a case study of a publicly‐funded small business incubator program, the Advanced Technology Development Center, located in Atlanta, Georgia. By explaining how the analysis is constructed and the results interpreted, the paper illustrates a potentially useful methodological approach to evaluating community economic development programs.  相似文献   

18.
通过对河北坝上地区菜田生长季节昆虫群落的系统调查,共得到9目42科269种48442个昆虫个体,比较了不同昆虫类群数量比例及优势种群季节变化规律,并分析了个体数、丰富度、多样性指数随季节变化的特点和机制。  相似文献   

19.
ABSTRACT This paper discusses various aspects of the economic analysis of commuting behavior. It starts with a review of two difficulties associated with urban economics models: the empirically falsified prediction of the relation between commuting time and income, and the presence of substantial excess commuting. Notwithstanding these anomalies, research that focuses directly on the value of travel time provides evidence that there is substantial resistance against commuting among large groups of workers. However, commuting costs are just one among many other explanatory variables for actual commuting behavior, and commuting itself has become much less onerous over time. This suggests that commuting costs play a much more limited role than has been assumed in the past. On the other hand, empirical evidence suggests that space is more important than one would be inclined to think on the basis of the considerations just given. These empirical regularities suggest that other space‐related aspects of the functioning of urban labor and housing markets are more important than was previously thought.  相似文献   

20.
《Growth and change》2005,36(4):584-587
The Porter Hypothesis and the Economic Consequences of Environmental Regulation , A Neo ‐Schumpetarian Approach
Edited by Thomas Roediger‐Schluga, Northampton, MA: Edward Elgar Publishing. 1704. 349 pp. $115.00 (Cloth). ISBN 1‐84376‐644‐247.
Reviewed by Cees Withagen
Department of Spatial Economics
Vrije Universiteit Amsterdam  相似文献   

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