An Application of spectral analysis in determining crop Rotation Frequencies

Spectral analysis has been applied many times in agricultural economics in determining harmonic characteristics of observed time series. However, spectral techniques have rarely been applied in conjunction with models which stress economic relationships. But two such empirical approaches are possible. One can use either frequency-domain regression of times series, i.e., general distributed lag estimation, in which time series of all important economic variables are considered [4, 5, 11], or one can use ordinary econometric estimation methods and then study frequency content of estimated disturbances with spectral techniques [1, Chapter 10]. The application of spectral analysis in this paper corresponds to the latter case. Ordinary time-domain (rather than frequency-domain) regression methods are used because the general lag relationship estimated here is not a case included in the general frequency-domain regression model. First, nonlinear regression techniques are used to explain the usual economic content of acreage supply response. Then estimated disturbances are investigated using spectral analysis to determine the importance of cyclic behavior in aggregate supply response. Specifically, this paper demonstrates how a cross section of time series may be pooled to obtain statisticaly significant findings when time series are short. These methods are demonstrated in an investigation of harmonic content in regression disturbances apparently due to crop rotation.     

基于改进引力模型的公租房空间布局适宜性评价——以重庆主城9区为例

研究目的：评价重庆主城9区21点公租房空间布局的适宜性并构建相应地评价指标体系和评价模型。研究方法：定性与定量结合,引力模型,GIS分析工具。研究结果：重庆主城9区21个公租房规划点适宜性程度总体较好;各个规划点的适宜性方向和程度存在差异;在空间分布上,呈现出“大分散、小集聚”的空间分布特征,即整体均匀分布,局部相对集中;评价结果与现实情况基本吻合。研究结论：基于改进引力模型构建的公租房空间布局适宜性评价指标体系和评价模型具有一定科学性和可行性;同时,对合理安排公租房的建设时序与建设进度提供参考性建议。     

A MODEL OF JOB CHOICE FOR THE ANALYSIS OF GOVERNMENT INTERVENTION IN STRUCTURAL ADJUSTMENT*

The paper presents a model of choice between alternative available jobs in which each job has an uncertain multi-period income prospect. Imperfectly informed expectations as well as job preferences and attitudes to risk determine the choice. The model is used to locate and discuss some problems of designing government programs which are intended to increase job mobility. The main conclusion is that government interventions may impose costs on the economy which are greater than the benefits because the information needed to assess costs and benefits is not generally available and political pressures may distort the expenditures.     

Pricing Weather Derivatives

This article presents a general method for pricing weather derivatives. Specification tests find that a temperature series for Fresno, CA follows a mean-reverting Brownian motion process with discrete jumps and autoregressive conditional heteroscedastic errors. Based on this process, we define an equilibrium pricing model for cooling degree day weather options. Comparing option prices estimated with three methods: a traditional burn-rate approach, a Black-Scholes-Merton approximation, and an equilibrium Monte Carlo simulation reveals significant differences. Equilibrium prices are preferred on theoretical grounds, so are used to demonstrate the usefulness of weather derivatives as risk management tools for California specialty crop growers.     

AN ADAPTIVE CONTROL APPROACH TO AGRICULTURAL POLICY*

It is postulated that some issues of economic policy in general, and of Australian agricultural policy in particular, may be analysed in the framework of an adaptive control model. Policy making is characterized as a rational, sequential decision-making process under conditions of imperfect knowledge in which forthcoming information may be used to learn about the uncertain terms as decision periods pass. Emphasis is given to the linear-quadratic control problem. The paper provides a review of the formulation of a policy problem in the framework of an adaptive control model and of derived policy strategies. An illustrative example is reported.     

森林资源可持续性宏观调控系统理论(三)——系统调控机制

森林资源可持续性宏观调控的目标是由若干既相互联系又具有一定层次的目标构成的目标体系。调控系统的主体是由政府的主要职能管理部门联合其他相关的职能部门共同组成的一个综合管理系统 ;调控的客体是森林资源的再生产过程。应用自然控制论原理探讨了森林资源可持续性宏观调控的系统优化控制模型。     

长株潭城市群一体化模式构建探索

首先,从空间布局、运作机制、组织管理、合作领域等方面阐述了国外城市群一体化的基本模式。进而,概括了长株潭城市群一体化实践探索所取得的成效。最后,构建了长株潭城市群一体化未来发展的"圈层式动态一体化模式",并对该模式内涵进行了全面的论述分析。     

基于资源环境约束下的休闲观光农业园游客满意度研究——以北戴河集发农业园为例

文章基于资源环境的约束,以北戴河集发休闲农业观光园为例,针对影响客户满意度的问题运用问卷调查法,即发放、搜集、收回和整理问卷,进行调查并数理统计。其中,高达95.8%问卷回收率,保障了问题研究所用数据的科学性、规范性和客观性。基于国、内外游客满意度的研究现状,在前人游客满意度分析模型研究基础上,根据实际所得数据建立了休闲农业观光园游客满意度分析模型——因子模型。因子模型是利用加权平均法计算权重函数的权重值,得到客户满意度的指标权重,对实际所得数据按照上述步骤处理,运用因子模型计算得到客户处于中等满意度的结论。该研究对因子模型进行了检验,证明了模型的有效性,提出了当前休闲农业发展的短板和需要提高的方面,为以后休闲农业的发展提供了侧重方向。     

A PORTFOLIO MODEL FOR EVALUATING RISK IN ECONOMIC DEVELOPMENT PROJECTS,WITH AN APPLICATION TO AGRICULTURE IN NIGER

After a literature review, a planning and project evaluation model is developed that includes both risk and profit considerations but avoids some weaknesses of other mean-variance models. Agricultural extension and project evaluation results of an application of this model are compared to those of the common profit-maximisation model. The two sets of results differ on the worth of intercropping, the relative merits of raising small ruminants and cattle, the likelihood of success of a major livestock development programme (which would benefit only wealthier farmers), the benefits of introducing labour-saving technologies, and the value of teaching/demonstration components in the projects being evaluated.     

电子商务背景下农产品F2F电商模式及其发展策略分析

由于信息交流不通畅、农产品价格波动频繁等原因,农产品电子商务在互联网技术发展带动下应运而生,各类农产品电商模式不断出现,其中农产品F2F电商模式就是最为重要的发展模式之一。文章通过归纳总结,从当前几种农产品电商模式特点出发,提出了农产品电商新模式——F2F(Farm to Family)。该文阐述了农产品F2F电商模式的运营模式内涵及当前发展现状,其次,剖析了F2F农产品模式的优劣点,最后根据前文分析,提出了积极构建农产品物流配送系统、积极培养农产品电子商务优秀人才、强化农产品的品质管理加快农产品电商发展的对策措施。     

Why Isn’t More US Farmland Organic?

We develop a theoretical model to assess the dollar compensation required to induce conventional growers to convert to organic. The model incorporates the uncertainty in producers’ expectations about future returns and about the impact of policy changes on these expectations in particular. We demonstrate that a new policy which favours organic can have opposing effects on the rate of conversion. An increase in relative returns to organic today will increase conversion rates. However, if the future of the policy programme is uncertain, its introduction can increase the value of waiting to switch, which will decrease conversion rates. We then develop an empirical switching regression model that enables direct estimation of the value associated with being able to postpone the conversion decision until some of the uncertainty is resolved. The model is applied to data on organic and conventional soybeans before and after major changes in US farm policy toward organic growers. The results suggest that sunk costs associated with conversion to organic coupled with uncertainty about future returns can help to explain why there is so little organic farmland in the USA.     

A partial adjustment model with rational expectations applied to the goat sector in Greece

In this paper an attempt is made to examine the rational expectations hypothesis for the goat-meat sector in Greece within the framework of a single equation method that describes the factors affecting demand and supply. The structural equations of the model are estimated by applying the Cochrane-Orcutt technique. The calculated elasticities suggest that Greek goat producers should pay more attention to milk rather than meat production. Statistical indications also confirm the effects of the Chernobyl accident upon the goat sector. Moreover, the forecasting ability of the model has been tested using simulation procedures, which indicate a small deviation between theoretical and observed values. Finally, some further implications concerning the goat sector are drawn from this analysis.     

The income earned by women: impacts on welfare outcomes

This paper provides an updated review of the evidence on income pooling across household members. Income pooling is one of the main predictions of the unitary model of the household. New studies come to much the same conclusion as do past studies: income pooling and the unitary model are rejected. The paper then looks beyond the mere rejection of the unitary model and explores some of the issues that arise. First, what is the progress in testing the restrictions imposed by non-unitary models of the household? Second, what are the implications of rejection of the unitary model for policy and program design? Finally, what are some of the challenges faced by programs and policies that internalize the rejection of income pooling in terms of impact evaluation?     

经验水蚀预报模型的国内外研究进展

土壤侵蚀预报模型是土壤侵蚀科学研究的重点内容之一,其中,水蚀模型又是土壤侵蚀定量研究的重要方法。国内外对水蚀预报模型已开展了大量的研究,取得了显著的进展和成果,经验水蚀预报模型受到众多学者的普遍关注,推动了该模型的不断完善和发展,对于水蚀预报、水土保持和水土资源持续利用有着重要的意义。论文在梳理大量文献基础上,对国内外水蚀预报模型发展进行了对比分析,以期为经验水蚀预报模型的进一步研究和应用提供参考。     

Welfare Effects of an Export Tax: Thailand's Rice Premium

An empirically based, applied general equilibrium model is used to study the welfare and distributional effects of an export tax when the implementing country possesses some monopoly power in the world market. A method is demonstrated through which a general equilibrium model can be used to find the optimal value of a tax or subsidy. The approach makes it possible to conduct the welfare analysis of a particular intervention in an explicit "second-best" context, to study its income distributional implications, and to explore the sensitivity of the results to variations in key behavioral parameters, structural assumptions, and the government's distributional objectives.     

IRREVERSIBLE SUPPLY FUNCTIONS REVISITED

This paper presents a successful application of an irreversible supply model to the UK egg sector. The model has been developed to overcome the problems that the conventional approaches to irreversible supply modelling face when used with a partial adjustment framework. The results indicate that the supply response to price changes under excess capacity is less than a third of that under non-excess capacity, but that the long-run response is symmetric, as required by the underlying theory. Furthermore, the long-run elasticity from a conventional, symmetric, partial-adjustment model is some 40% larger than that of the asymmetric model, implying that the importance of the asymmetric specification extends beyond an interest in the short-run adjustment path.     

驻马店城区用地扩展评价

通过分析影响驻马店城市用地扩展的主要因素,建立了驻马店城区扩展评价指标体系,并且采用多目标突变决策评价法进行了驻马店城区扩展方向评价,科学性较强,避免了定性分析的不足,对驻马店市的今后发展具有参考意义.     

新疆农业保险效率的实证研究——基于SE-SBM-DEA和Tobit模型的分析

[目的]文章以干旱地区新疆为例,通过选择新疆农业各类别中作物种植面积较大的种植品种及养殖业种类,综合测算2008~2013年新疆农业保险效率水平。[方法]运用SE-SBM-DEA模型,从技术效率、纯技术效率、规模效率3方面对新疆农业保险效率进行实证研究,分析技术效率、纯技术效率和规模效率均与经济增长水平之间的关系,同时运用Tobit模型分析影响技术效率的宏观经济因素。[结果]新疆地区整体上保险效率较高,其中养殖业保险效率高于种植业;农业保险发展不均衡,种植面积和风险均较大的玉米、棉花、仁果类作物的保险效率较低,而种植比重相对不高、风险偏低的甜菜、蔬菜等作物的农业保险效率较高;另外养殖业保险效率水平较高,其中羊的养殖保险规模效率达到最优。[结论]基于此,进一步对影响保险效率的宏观经济因素进行分析并提出相应的政策及建议。     

COMPROMISE-RISK PROGRAMMING FOR AGRICULTURAL RESOURCE ALLOCATION PROBLEMS: AN ILLUSTRATION

This paper presents a novel approach for dealing with risk in agricultural resource allocation decisions by synthesising the conventional Markowitzean, or MOTAD, methods within a compromise programming model to generate ‘best-compromise’ solutions which come closest to an ideal point defined in terms of risk minimisation. This approach can be regarded as the compromise-risk programming model. The purpose here is to show how this ‘hybridisation’ of Markowitz/MOTAD and compromise programming approaches overcomes some of the weaknesses of the traditional approach to handling risk in resource allocation models.     

Are "Decoupled" Farm Program Payments Really Decoupled? An Empirical Evaluation

This analysis utilizes farm-level data to evaluate the extent to which U.S. farm program benefits, particularly direct payments, bring about distortions in production. The issue is important in WTO negotiations and in the debate over the distortionary effects of decoupled ("green-box") payments. Our results suggest that the distortions brought about by AMTA payments, though statistically significant in some cases, are very modest. Larger effects are implied for market loss assistance payments. Probit models suggest that AMTA payments do not influence the likelihood that agents will acquire more land. Our results are reinforced using an aggregate county-level acreage model.