Investigating the performance of different estimation techniques for crop yield data analysis in crop insurance applications

We investigate the performance of the ordinary least squares (OLS)‐, M‐, MM‐, and the Theil–Sen (TS)‐estimator for crop yield data analysis in crop insurance applications using Monte Carlo simulations. More specifically, the performance is assessed with respect to trend estimation, prediction of future yield levels, and the estimation of expected indemnity payments. In agreement with earlier findings, other estimators are found to be superior to OLS in simple regression problems if yield distributions are outlier contaminated and heteroscedastic. While this conclusion is also valid for subsequent applications such as yield prediction and the estimation of expected indemnity payments, the difference between the considered estimators becomes less distinct. For these applications, we find particularly the M‐estimator to be a good compromise between high‐breakdown (very robust) estimators and the very efficient OLS‐estimator. Because no regression technique dominates all others in all applications and scenarios for error term distributions, our results underline that the choice of the estimation technique should be dependent on the purpose of the crop yield data analysis. However, alternative estimators such as M‐, MM‐, and TS‐estimator can reduce (and bound) the risk of unreliable or inefficient crop yield data analysis in crop insurance applications.     

Editorial

An Almost Ideal Demand System (AIDS) was utilized to model the United States demand for domestic and imported tobaccos. The model, which includes equations for domestic flue-cured tobacco, domestic air-cured (burley) tobacco, oriental tobacco, and imported flue-cured and burley tobacco, incorporates the impact of economic factors as well as changes in consumer tastes. In this model homogeneity was rejected under certain conditions, but symmetry could not be rejected. These results suggest that imported flue-cured and burley tobacco, to a limited extent, is a substitute for domestic flue-cured tobacco and is a complement for domestic air-cured tobacco. The trend toward lower average nicotine content of domestic cigarettes is shown to have a detrimenta1 effect on the demand for domestic flue-cured tobacco, but a beneficial impact on domestic air-cured (burley), and imported oriental tobaccos.     

Ranking Crop Yield Models: A Comment

This comment discusses key specification issues that may have affected the performance and, therefore, the ranking of parametric models that were compared in a recent AJAE article. A procedure to obtain the most flexible parametric model specification possible, given the particular probability distribution function on which the model is based is presented. These specifications also allow for standardized and, therefore, more valid comparisons across parametric models that are based on different probability distributions. Finally, the comment cautions against generalization of the rankings in that AJAE article and recommends that these more flexible specifications be adopted in future comparisons and applications.     

废弃矿山土地复垦投资及收益分配探讨

废弃矿山土地投资收益分配要遵循市场分配规律,按照投入要素的贡献大小分配收益。国有土地上废弃矿山投资收益分配：单个投资者投入,投资收益归该投资者所有;多个投资者投入,按照投入要素和贡献多少来进行收益分配。政府和投资者之间的收益分配：政府可以对国有土地上的废弃矿山收取较低的土地使用权费用或税收。集体所有土地上废弃矿山投资收益分配：投资集体土地上的单位或个人以租金或土地承包金的方式获得废弃矿山土地的使用权或将集体土地作价入股;单位或者个人可以对废弃矿山土地进行前期开发向集体收取复垦费用。     

What is the policy improvement of China’s land consolidation? Evidence from completed land consolidation projects in Shaanxi Province

Land consolidation plays an important role in increasing cultivated land, improving cultivated land quality and the ecological environment, and promoting the coordinated development of urban and rural areas. However, under the conditions of three decades of land consolidation being conducted and changing urban–rural human–land relationship, the areas of improvement in the land consolidation policy of China must be studied. This article analyzes the implementation and distribution characteristics of the land consolidation project completed in Shaanxi Province in 2018. Results show that land consolidation projects in Shaanxi are mainly land reclamation projects, cropland consolidation projects, and high-standard cropland consolidation projects. The increased cultivated land is mainly from land reclamation projects and cropland consolidation projects. The land consolidation projects in Aeolian Plateau Area, Loess Plateau Area, and Da Ba Mountain Area are mainly land reclamation projects. The land reclamation projects in Guan Zhong Plain Area and Qing Ling Mountain Area account for a large proportion. The spatial distribution of rural settlement consolidation projects, and rural settlement consolidation and land reclamation projects are mainly located in Guan Zhong Plain Area and distributed in the boundary area of Guan Zhong Plain Area and Loess Plateau Area. According to the characteristics of land consolidation projects and the changes of urban–rural human–land relationship, China should be prudent in or stop advancing land reclamation to increase cultivated land; cropland consolidation and high-standard cropland construction are vital ways to achieve China’s food security; and rural settlement consolidation should be carefully conducted in remote areas under the background of urbanization.     

农牧户生计资本对农畜产品销售渠道选择影响研究

[目的]优化农畜产品销售渠道,提高农牧民收入,是乡村振兴战略不可或缺的实施路径。文章通过对内蒙古农牧户生计资本进行测算与分析,探究不同生计类型农牧户生计资本与其农畜产品销售渠道选择间的互馈关系,精准识别不同类型农牧户选择销售渠道的影响因素,旨在优化民族地区乡村农畜产品流通渠道,助力民族地区乡村振兴。[方法]文章基于可持续生计理论(DFID),以微观农牧户视角,从自然资本、人力资本、物质资本、金融资本、社会资本5个维度,运用农牧户生计量化法和模糊层次分析法(FAHP)、Multivariate Logistic模型、多元线性回归实证研究。[结果](1)不同类型农牧户生计资本存量具有显著差异,生计资本由高到低排序为:半农半牧户纯农户纯牧户;(2)农牧户对农畜产品销售渠道选择比例由高到低排序为:中间商、批发市场、零售市场、合作社、订单销售、超市直供,传统卖给中间商依然是内蒙古地区农畜产品流通渠道的主要模式,且不同销售渠道之间存在互补与竞争关系;(3)农牧户生计资本对其选择销售渠道具有显著影响,影响力由高到低排序为:人力资本自然资本金融资本社会资本物质资本;(4)不同维度生计资本对不同类型农牧户的农畜产品销售渠道的选择影响程度具有显著差异,影响农牧户选择销售渠道的首要因子是人力资本,影响牧户选择的首要因子是金融资本,影响半农半牧户选择的首要因子是社会资本与人力资本。[结论]该文提出基于农牧户生计资本视角的民族地区乡村农畜产品销售渠道优化对策与建议,一定程度上破解了不同类型农牧户在农畜产品销售渠道选择时遇到的困境。     

重庆市乡村旅游资源空间特征及其与乡村振兴关系研究

[目的]探究重庆市乡村旅游资源的结构类型和空间特征,分析乡村旅游资源数量与乡村振兴之间的关系,对重庆市乡村旅游产业发展和促进乡村振兴具有指导意义。[方法]文章利用GIS技术定量分析重庆市乡村旅游资源的空间分布特征,通过空间分布模型探究乡村旅游资源空间分布的聚集程度,利用地理联系率探析人口规模和经济发展水平与乡村旅游资源分布的配合度。采用回归模型从整体上对重庆市乡村旅游资源数量与乡村振兴的关系进行分析,利用Pearson相关系数对不同经济发展区域关系进行研究,试图得到乡村旅游资源数量与乡村振兴的辩证关系。[结果]重庆市乡村旅游资源具有4种类型,农事体验类所占的比重最大,达到43.46%,乡村文化类所占比重最低为2.30%。乡村旅游空间布局特征结果表明重庆市4种乡村旅游类型在空间上的分布存在较大的区域差异,都呈现集中分布, 4种类型的景点与人口和经济的配合度较高。回归分析结果表明,乡村旅游资源数量与休闲农业和乡村旅游接待人次、农村卫生厕所普及率、村综合性文化服务中心覆盖率、县级以上文明村和乡镇占比和农村居民人均纯收入之间存在均衡关系。Pearson相关性分析结果表明除休闲农业和乡村旅游接待人次外,乡村旅游资源数量仅与农村居民人均纯收入之间存在低度相关性,不同经济区相关系数差异较大。[结论]综合以上研究结果,乡村旅游资源的空间分布特征既受当地经济发展的影响,同时又促进当地经济的发展,表明重庆市乡村旅游资源对乡村振兴具有一定的促进作用。建议在今后的发展中应拓展乡村旅游类型,提高乡村文化类景点的数量和比重,促进重庆市乡村旅游产业的均衡发展,实现不同经济区乡村经济的协调发展。     

基于POI提取的山地丘陵区乡村旅游空间分布研究*——以重庆市农家乐为例

［目的］通过大数据研究山地丘陵区乡村旅游的空间分布现状及规律,为乡村旅游规划提供参考借鉴。［方法］基于POI抓取技术,以2018年9月抓取到的重庆市1 644家农家乐为研究对象,结合各种地理基础数据资料,借助GIS分析手段,采用最近邻指数、K函数、核密度估计、Getis Ord Gi*热点分析和Moran′s I指数对重庆市农家乐空间分布特征进行研究。［结果］（1）重庆市农家乐分布整体呈现显著聚集趋势,空间自相关性显著; 主城区为聚集—随机分布,空间自相关性不显著; （2）市域范围农家乐聚集程度随空间尺度的增大而增强,主城区特征空间尺度为2139km; （3）农家乐在中部主城区集中连片分布,在主城外零散分布; （4）全市农家乐分布热点区域集中在中南部; （5）7044%的农家乐分布在距城市中心120km的范围内; （6）767%的农家乐分布在A级景区周边10km范围内,且倾向于分布在自然类景区和高等级景区周边; （7）中海拔地区为农家乐分布的主要区域。［结论］提出针对性的改善建议,以优化农家乐产业布局,促进乡村旅游发展与生态文明建设充分结合,更好助力乡村振兴。     

基于AHP的耕地保护公共政策分析

耕地保护是我国的一项基本国策,在执行耕地保护政策过程中出现了"自上而下"、"激励主体"两种不同的保护模式,不同模式政策执行效果有显著差异。耕地保护制度在执行过程中经常出现偏差,中央政府保护耕地的政策目标不能得到有效实现,耕地保护的主体——农户的基本利益也不能满足,耕地质量的隐形下降与保护效果的明显欠佳。这些现象都表明需要客观评价不同模式的耕地保护政策。河北是农业大省,唐山市是其经济发达、耕地保护任务艰巨的典型地区。根据唐山市典型农村356家农户进行实地调查获取的数据和资料,选取评价指标和因素,运用层次分析法对"自上而下"、"激励主体"两种不同模式的耕地保护政策执行效果进行对比分析。研究表明,"激励主体"的耕地保护模式在执行效果上显著优于"自上而下"的耕地保护模式。研究结论表明需要从"自上而下"的行政模式向以经济激励为核心"激励主体"的市场模式转变,这对优化耕地保护政策执行具有借鉴意义。     

伊犁河谷地区种植业产业布局调整与优化研究——以伊宁县为例

坚持"高产、优质、高效、生态、安全"的发展方向,加快种植业产业布局调整,对于增强伊犁河谷地区农业综合生产能力、确保粮食安全及农产品的有效供给有着重要意义。伊宁县是伊犁河谷地区具有代表性的农业大县,文章以伊宁县为例,在分析伊宁县种植业产业发展现状的基础上,结合伊宁县内外农业产业化的发展需求,提出"稳定小麦,提质玉米,增加果蔬"的调整思路。采取综合比较优势指数法从效率优势、规模优势及综合优势3方面对伊宁县种植业主要农作物类型与全国同类农作物进行优势比较分析,并结合GIS软件的空间分析功能,将伊宁县划分为农业种植三大功能区,围绕伊宁县农业优势支柱产业和特色农产品规模化生产,建成优质高效、高产出率和高商品率的六大特色农产品标准化生产基地,形成万亩连片示范片和万亩示范田,促进农业生产布局区域化、生产规模化、经营一体化,满足农业的发展需求。