Timber price dynamics after a natural disaster: Hurricane Hugo revisited

Timber prices in the area struck by a natural disaster such as a hurricane or pest infestation are known to drop sharply immediately following the disaster, only to recover after about a year or so. Previous research attributes the rapid recovery to shifts in supply and demand curves. Our analysis suggests the more probable explanation is rotation in the curves. Supply and demand shifts come into play in the second and third years as rebuilding from the hurricane begins in earnest, and as timber inventory is rebuilt in response to elevated price expectations. But for the period in which price recovery occurs, model simulations based on data for Hurricane Hugo indicate the major causal factors of the observed price dynamics are curve rotation and trade with the surrounding undamaged region. Inventory-based supply shifts, the previously-identified causal factor, play a minor role in the observed price dynamics. Getting the causal factors right is important for predicting the price effects of forest inventory shocks, and for proper measurement of their welfare effects.     

基于灰色系统模型的城乡建设用地规模预测——以济南市为例

建设用地规模预测是土地利用总体规划编制的核心,也是土地利用管理的依据。为了切实搞好济南市的土地利用总体规划,使之更具有前瞻性、可操作性,必须切合实际地搞好建设用地需求规模和布局的预测。采用灰色系统模型,通过灰色关联度分析,建设用地发展与GDP、总人口、市镇人口、社会固定资产投资、第二产业产值、第三产业产值密切相关。基于这些因子,采用灰色系统模型法、建立GM(1,1)灰色模型,进行了2015年和2020年城乡建设用地规模的预测。     

建设用地供应规模与结构对城市发展质量的影响研究

研究目的:分析建设用地供应规模、建设用地供应结构变化对城市发展质量的影响效应,为以提高质量为导向的新型城镇化战略提供参考。研究方法:采用构建综合指标体系的熵值法测度城市发展质量,运用空间计量模型对土地供给与城市发展质量的相关性进行验证分析。研究结果:无论是建设用地供应规模,还是建设用地供应结构(工业用地占比、商业用地占比、住宅用地占比、公共管理与公共服务用地占比),均与城市发展质量之间存在倒U型曲线变换关系,即建设用地供应规模和建设用地供应结构在服务于城市高质量发展的时候,均存在一个动态的最优值或者最优比例。研究结论:建设用地供应对城市发展质量的影响是动态调整的,需要根据建设用地供应和城市发展质量的实际情况来确定最优的建设用地供应规模和供应结构。     

我国农业生产“服务规模化”对“土地规模化”的影响——替代与互补关系解释

目的 推动农业规模化经营是我国农业现代化发展的基本要求。文章旨在厘清我国农业生产“服务规模化”与“土地规模化”二者之间的替代抑或互补关系，以实现粮食总产最大化的目标。方法 文章以农机服务为研究切入点，采用随机前沿生产函数模型和门槛效应模型，探讨农机服务对粮食总产、播种面积的影响，以及不同土地规模下农机服务对粮食总产的影响程度。结果 研究结果表明，增加农机服务投入会提高粮食单产以及播种面积，且农机服务与农户土地经营规模表现出阶段性的变化特征，农机服务对粮食生产的影响程度会随着土地经营规模的增加而先下降后扩大，即“服务规模化”的作用会受到“土地规模化”发展的约束，虽然“服务规模化”能够在一定时期内、一定程度上替代“土地规模化”的不足或相对滞后，但是“服务规模化”的生产效应又依赖于“土地规模化”程度的发展。结论 基于以上研究，该文建议，在推动我国农业规模化的过程中，应当阶段性的和差异性的采取“服务规模化”和“土地规模化”两种路径方式，充分利用二者互为补充以及相互替代的关系，以实现多种形式的适度规模经营。     

Credit Risk and the Demand for Agricultural Loans

This paper uses the lender–borrower relationship to provide insight into the impirical estimation of loan demand/contract curves for agricultural loans. Loan demand is shown to be determined partly by lenders'willingness to provide debt. The implicit solution to the loan contract curve in the lender–borrower relationship is derived from the cumulative probability distribution function of loan losses, which is the same measure used as the dependent variable in credit scoring models. Consequently, empirical estimation of loan demand can be obtained from credit scoring models. This paper presents the theory and then provides loan demand estimates and elasticities using Farm Credit Corporation cross-sectional and time-series data. Empirical estimates indicate the possibility of a backward-bending loan demand curve, which may indicate some credit ationing in agriculture.     

农户土地经营规模与粮食生产效率关系实证研究

研究目的:确定农户土地经营规模与粮食生产效率之间是否存在显著关系,如果存在,则是怎样的一个关系。研究方法:访谈调查法,相关分析法,聚类分析法和DEA分析法——BCC(VRS)。研究结果:农户土地经营规模与粮食生产效率之间不是简单的正向或负向的线性关系。研究结论:在一定规模范围内,农户粮食生产效率随土地经营规模的扩大呈现U型曲线的变化规律;过于狭小的土地经营规模使得绝大多数粮农家庭规模报酬递增显著,其粮食增产增效具有较强的上升潜能;农户存在大量的劳动剩余,家庭从事非农产业用工量的适当增加反而对粮食生产效率提高具有一定的促进作用。     

渔业上市公司规模经济效应研究——基于C-D和DEA模型分析

以十三家渔业上市公司的规模经济效应为主要研究对象,运用柯布-道格拉斯生产函数模型检验渔业企业所处的规模经济阶段,同时运用数据包络分析模型分析渔业企业的规模经济系数。结果表明,我国渔业企业整体处于规模报酬递减阶段,大多数企业处于非DEA有效状态。建议适当降低劳动力投入比例,加大相关研发投入力度,提高对规模经济效应的认识,充分发挥资本对企业生产经营的积极影响。     

An econometric analysis of demand for food quantity and quality in urban China

This article offers an analytical framework for studying consumer demand for food quality based on a theory‐consistent demand model, namely, the Exact Affine Stone Index specification. Importantly, it accounts for unobserved consumer and regional heterogeneity, and allows for arbitrary Engel curves. The empirical value of our framework is illustrated in an econometric analysis of demand for food quality in China. Evaluating possible structural changes in consumer food expenditures in China is of paramount importance, given the ever‐increasing global role of China and the implications of the structural food preference changes for the global food system. The major findings emerging from this study indicate that income is an important determinant of demand for food quality and quantity with the relatively more affluent provinces having a higher affinity for food quality.     

粮食安全视角下粮食主产区耕地休耕规模及动态仿真研究

研究目的:以保障粮食安全为目标,构建粮食主产区休耕最大规模测算和仿真模型,仿真预测不同人口政策效应情景下最大休耕规模及休耕规模弹性边界,以期为保障中国休耕政策推行的科学性和合理性提供参考.研究方法:系统动力学模型.研究结果:(1)2007—2016年模拟期内,湖北省在兼顾区域粮食供给和保障国家粮食安全的同时,能够保有一定比例持续增长的弹性耕地资源,支撑国家"藏粮于地"战略的实施;(2)2017—2036年仿真期内,湖北省休耕最大规模和休耕规模弹性边界在人口增长保持不变和不断下降两种情景下总体保持扩张趋势,在人口增幅略微上升和大幅上升两种情景下呈现先缩小再扩大的态势;(3)在当前符合全面二孩政策目标人群规模庞大且妇女二孩生育意愿较强的情况下,全面二孩政策在中长期的粮食需求增加效应极有可能导致湖北省可休耕耕地规模减少和休耕规模弹性边界缩小.研究结论:应积极扩大休耕规模和范围,丰富休耕试点区域,正式建立目标多元化、模式多样化和实施常态化的耕地休耕制度,以粮食安全为前提实现对休耕的宏观调控.     

REDUCING THE NITROGEN INPUT ON ARABLE FARMS

Nitrogen response curves derived from experimental data are used with a profit maximising condition to obtain optimum N rates, yields and gross margin losses for a range of nitrogen and cereal prices. These results are used with a linear programming model of an arable farm to estimate changes in the optimal cropping allocation and hence the farm scale effects of relative price changes. Total nitrogen applied is found to have a limited response: a doubling of the N price reduces the total used by between 24% and 10% depending on the availability of low-N break-crops. Cereal price changes reduce profitability severely before having any significant effect on N use.     

太仓市区城镇用地扩展合理规模计量研究

研究目的：探讨规划目标年城镇用地合理规模及其测算方法,为经济发展与耕地保护“两难”问题的解决提供依据。研究方法：采用C-D生产函数及成本效益曲线分析城镇用地合理规模条件,进而通过加权最小二乘法估计城镇用地合理规模测算模型,并结合情景分析法测算不同经济发展条件下规划目标年城镇用地合理规模。研究结果：在考虑生态服务价值时,社会经济中速发展下太仓市区2015 年及2020 年城镇用地合理规模分别为4805.61 hm2 和5495.88 hm2 ,此情景较为合理;而高速经济发展下2015 年及2020 年城镇用地合理规模为5133.36 hm2 和6161.38 hm2 ; 如果不考虑生态服务价值,则在中速发展时2015 年及2020 年城镇用地合理规模为5907.38 hm2 和6756.93 hm2。研究结论：通过经济计量模型及情景分析法等可以确定未来一定社会经济发展情景下不同年份的城镇用地合理规模。     

耕地保护规模测算方法研究——以湖北省为例

目前,土地利用总体规划中预测耕地保护规模,主要是通过粮食作物需求量来预测耕地的需求量,然后根据耕地的供给量来分析供需平衡,确定耕地保护的规模.测算方法存在方法单一、科学性不强、预测性不够等缺点,不能较好的预测未来耕地变化趋势.在湖北省土地利用总体规划修编专题研究中,为了避免上述方法带来的缺陷,采用了基于粮食安全需求预测方法、趋势外推法、剩余法和社会经济目标预测法等来测算耕地保护的规模,然后定性的分析各种方法的准确性,并分别赋予每种方法预测结果不同的权重综合确定耕地保护规模.     

A Family of Differential Input Demand Systems with Application to Greek Agriculture

This paper develops a family of input demand systems via alternative parametrisations of Theil's differential model. Each member of this family is as flexible as any other locally flexible functional form. More importantly, selection among the competing family members is possible via simple parameter restrictions. The family of differential input demand systems is applied to the agricultural sector in Greece for the period 1961–96. Formal tests suggest that the model with the CBS-type effects dominates the alternative models. Divisia and price elasticities are calculated from the selected model and a decomposition of changes in the demand for inputs into technical change, total input volume, substitution, and residual effects is performed. The empirical results are quite reasonable. Overall, the analysis in this paper indicates that, in certain cases, the differential approach may provide an attractive alternative to the dual approach in modelling production behaviour.     

农户林地未流转行为影响因素分析

主要从实证角度论证了农户未流转行为的三方面关系。其中,运用Logistic回归模型所得出的结果显示林地经营规模影响农户对林地的需求,但不影响农户对林地的供给,且与农户的未流入行为为非线性关系;资金状况显著影响农户的未流入行为,而家庭非农收入比重并不显著影响农户的未流出行为;林业服务状况对未流入和未流出行为有不同程度的作用。因此,为促进林地的流转应主要解决好资金和服务体系建设两大问题。     

规模化养猪业的环境风险研究

目的 随着农业现代化步伐的不断加快,农业规模化生产模式已成为一种重要的经营模式被普及和推广。农业规模化经营模式具有高效率、规模效益等特点,但也可能产生一些难以预见的社会问题,如环境污染。从权力—资本的逻辑来看,规模化养殖模式具有更高的经济效益并更利于政府开展环境管理与监督,且在政策扶持与财政资助方面更有针对性,有助于政府从整体上来管控规模化养殖企业。方法 文章通过现场查看、深度访谈等实地调查及比色法水质检测方法来开展研究。结果 研究发现大规模养猪场的畜禽排泄物所造成的环境污染在不断加重,环境风险发生的可能性也在增加。相反各种中小型养殖户、散养户的养殖模式却与地方社会结合得更好,养殖点分布广泛且周边环境的净化能力强,不仅具有较高的经济价值,也较好地保护了周边环境,更具有可行性和操作性。结论 依据不同逻辑形成的养猪模式产生了截然不同的环境效应。养殖规模应基于不同地域、不同的经营方式来设定,形成适度规模的养殖模式。     

Shadow pricing diversity in U. S. national forests

Tobit estimation of the market value of timber sales in national forests of North Carolina demonstrates the important effect of stand diversity on the formulation of bid prices for mixed-species timber tracts. The hedonic model generates a shadow price for diversity according to changes in bid prices, an effective shift in the demand curve for auctioned tracts due to stand diversity attributes. This approach contrasts with traditional shadow price analyses that focus on the supply effects of environmental constraints. Results are corrected for the effects of bidder participation, market conditions, production costs, and other stand attributes. Econometric results demonstrate that stand heterogeneity is a highly significant factor influencing the market value of timber sales from national forests of the Appalachian region. Greater heterogeneity results in lower bid prices for timber sales, indicating a positive shadow price for maintenance of stand diversity.     

人民币汇率变动对我国水产品贸易的影响

水产品外贸在我国外贸、特别是在农产品外贸中占有重要的地位。本文在论述了人民币升值对水产品贸易影响的一般原理和过程的基础上，讨论了人民币汇率变动对水产品贸易所产生的其他效应，包括：对于加工贸易和当进出口商品需求弹性之和小于1时，人民币升值会促进出口；人民币升值有利于改善我国水产品的贸易条件，使社会福利增加；人民币升值会使我国水产品贸易规模增大。最后本文给出了结论与建议。     

Demand System Estimation with Upward-Sloping Supply

There are three important implications of this work. First, demand systems estimates that overlook supply response are as subject to simultaneous equations bias as single ad hoc demand equations. Theil shows theoretically that assuming supply curves are perfectly elastic, when in fact they are not will underestimate price responsiveness in demand equations. An empirical example is presented that demonstrates that the price elasticities generally increase when upward-sloping supplies are assumed.
Second, the iterative testing procedure presented may provide direction for model building when the true structure of the system is unknown. For example, the results of the Wu-Hausman test indicate that assuming chicken supply is perfectly elastic in a model of the Japanese livestock industry is justified. The results also indicate that the supplies of Wagyu beef, dairy beef, pork and fish are upward-sloping and therefore should be modeled as endogenous variables in the demand system.
Third, the results emphasize the sensitivity of projections of Japanese beef imports to the assumptions underlying the demand system. If perfectly elastic meat supplies are assumed for an analysis of reducing Japanese beef import liberalization, the results will likely underestimate the impacts on beef imports.
In summary, the supply curves for agricultural products tend to slope upward within the time periods used for traditional policy analysis and demand system estimation, which in turn implies that prices are determined endogenously within the system. Endogenous price determination is contrary to the assumptions that underlie the theoretical foundations and many empirical applications of demand systems. We present a methodology to test for and adjust demand systems for endogeneity. The importance of this adjustment is demonstrated by using an analysis of the liberalization of the Japanese beef market.     

新型农业经营主体农机作业服务的双重角色及其动态转变:一个初步的分析框架

近年来新型农业经营主体在发展壮大过程中围绕典型的农机作业服务,表现出从服务需求者向服务供给者转变的动态特征,但现有研究未将此双重角色置于统一的分析框架中,呈现着割裂的研究状态,缺乏对角色转变的逻辑阐释。鉴于此,本文在角色转变的动态视角之下,以农地经营规模变化表征新型农业经营主体的成长过程,通过分析新型农业经营主体在不同农地规模阶段购买和供给农机作业服务所面临的交易成本的变化及其影响,构建探寻双重角色的形成机制和转变逻辑的分析框架。     

Estimation of Profit Functions When Profit is Not Maximum

This paper deals with derivation and implications of profit functions when profit is not maximum due to the presence of either technical inefficiency or allocative inefficiency, or both. We show that input demand and output supply, elasticities, and returns to scale are, in general, affected by these inefficiencies. We also show that the overall profit efficiency is not necessarily the product of technical and allocative efficiencies, meaning that technical and allocative inefficiencies are not necessarily independent. Estimation techniques are developed for both cross-sectional and panel data models. Working of the model is illustrated using a panel of 60 salmon farms.