大数据时代下电子商务平台的探索和研究——以淘宝网为例

随着网络用户的日益增长,互联网记录着大量的用户个人信息和由智能终端产生的图片和信息,这些信息爆炸性的增长,并不断涌入网络海洋,产生海量的数据信息。在电子商务环境中大数据处理将会发展出更多强大和多元的功能。本文以淘宝网为例,分析研究如何合理利用数据,为企业的经营模式做出相应调整,并且在变化中不断进行企业新技术、新方法和新思路的探索。同时指出数据泄露的隐患,并给出相应建议。     

玉米产后流通中减损降耗需重点关注的两个环节

玉米是我国主要粮食品种,在不断提高产量的同时,研究减少玉米产后损失,降低粮食损耗和流通成本,对于确保粮食安全和提高玉米原粮品质具有重要的作用。     

我国玉米价格与生猪价格的传导关系研究

现以2015年1月到2020年9月生猪价格和玉米价格的月度数据为研究对象,运用E-G协整检验、格兰杰因果关系检验、脉冲响应、方差分解等方法进行分析。研究结果表明,生猪价格和玉米价格存在长期正相关的均衡关系,生猪价格对玉米价格有明显的拉动作用;短期内,玉米价格和生猪价格的相互影响具有时滞性。长期来看,当生猪价格受到冲击时,对玉米价格的影响作用相对较小;当玉米价格受到冲击时,对生猪价格的影响作用较大。建议保障玉米和生猪的供给,引导供需平衡;完善信息共享机制,及时传递相关信息。     

Land Tenure and the Adoption of Conservation Practices

We use a logit adoption model with data on 941 U.S. corn producers from the 1996 Agricultural Resource Management Study to analyze the influence of land tenure on the adoption of conservation practices. We extend previous analyses by distinguishing renters according to lease type and by distinguishing practices according to the timing of costs and returns. We find that cash-renters are less likely than owner-operators to use conservation tillage, but share-renters are not. Both cash-renters and share-renters are less likely than owner-operators to adopt practices that provide benefits only over the longer term (grassed waterways, stripcropping, and contour farming).     

基于Nerlove模型的中国不同区域玉米供给反应研究

针对我国玉米生产区域差异较大的特点,把全国分为三个玉米生产区域,构建了玉米单产和玉米种植面积供给反应模型,进而对我国玉米供给反应进行研究,并测算了我国玉米供给的面积弹性和单产弹性。研究结果表明,不论在长期弹性还是短期弹性方面,玉米种植面积弹性均优于玉米单产弹性。     

玉米期货价格收益率和波动性的实证研究——以中国大连与美国CBOT市场为例

采用协整模型、Granger因果关系检验、误差修正（EC）模型及几种GARCH模型对中国大连与美国CBOT的玉米期货价格及收益率和波动性进行了实证研究。分析发现：两市期货价格之间存在双向的Granger因果关系和显著的协整关系;两个市场之间存在显著的同向变动关系,存在长期的共同趋势;EC模型反映出两市的长期期货价格收益率没有显著差异,两市均受到对方市场期货价格收益率的影响,但短期波动过程则存在一定的差异。此外,通过建立GARCH类模型发现：两市在波动性的传导和影响上存在一定程度的非对称性;两市均存在溢出效应与一定的杠杆效应,大连玉米期货市场对CBOT玉米期货市场的溢出效应显著存在,而CBOT玉米期货市场对大连玉米期货市场的溢出效应不显著存在,市场的波动性对消息影响呈现一定程度的非对称性。由此可见,大连玉米期货价格已经具备了较强的国际定价功能。     

中国玉米期货市场的价格引导作用究竟有多大?——基于VECM模型的实证分析

基于Johansen协整分析、向量误差修正模型(VECM)以及方差分解等计量分析方法对中国的玉米期货市场、玉米现货市场、CBOT玉米期货市场以及中国大豆期货市场四者之间的动态关系与相互冲击机制进行了深入的研究。研究发现:四个市场的一阶非平稳的时间序列构成了协整关系,即它们之间具备了长期均衡关系,中国玉米期货市场对现货市场以及存在关联性的大豆期货市场具有良好的价格发现与引导功能。但是由于我国玉米产业对外开放程度不够,所以我国的玉米期货在国际玉米定价体系中还没有达到支配性的地位。     

Ecosystem impacts of pesticide reductions through Bt cotton adoption

This article examines the ecosystem impacts of transgenic Bt cotton technology resulting from reduced chemical pesticide use. Employing unique panel data from smallholder farmers in India, negative environmental and health effects of pesticide use are quantified with the environmental impact quotient (EIQ), with and without Bt technology. An environmentally sensitive dynamic production function is estimated, treating the environmental risk of pesticide toxicity as an undesirable output in the production process. Negative externalities are significantly lower in Bt than in conventional cotton. The reduction in EIQ through Bt technology adoption has increased from 39 per cent during 2002–2004 to 68 per cent during 2006–2008. Bt adoption has also contributed to higher environmental efficiency. Environmental efficiency is influenced by the quality of Bt technology: high‐quality Bt seeds are associated with higher environmental efficiency than lower‐quality seeds.     

A Question of Integrity: Variants of Bt Cotton,Pesticides and Productivity in Pakistan

Bt cotton remains one of the most widely grown biotech crops among smallholder farmers in lower income countries, and numerous studies attest to its advantages. However, the effectiveness of Bt toxin, which depends on many technical constraints, is heterogeneous. In Pakistan, the diffusion of Bt cotton occurred despite a weak regulatory system and without seed quality control; whether or not many varieties sold as Bt are in fact Bt is also questionable. We utilise nationally representative sample data to test the effects of Bt cotton use on productivity. Unlike previous studies, we invoke several indicators of Bt identity: variety name, official approval status, farmer belief, laboratory tests of Bt presence in plant tissue, and biophysical assays measuring Bt effectiveness. Only farmer belief affects cotton productivity in the standard production model, which does not treat Bt appropriately as damage‐abating. In the damage control framework, all Bt indicators reduce damage from pests. Biophysical indicators have the largest effect and official approval has the weakest. Findings have implications for impact measurement. For policy‐makers, they suggest the need, on ethical and productivity grounds, to improve variety information and monitor variety integrity closer to point of sale.     

The Costs of Coexistence Measures for Genetically Modified Maize in Germany

We estimate the perceived costs of legal requirements (‘coexistence measures’) for growing genetically modified (GM) Bt maize in Germany using a choice experiment. The costs of the evaluated ex‐ante and ex‐post coexistence measures range from zero to more than €300 per measure and most are greater than the extra revenue the farmers in our survey expect from growing Bt maize or than estimates in the literature. The cost estimates for temporal separation, the highest in our evaluation, imply that the exclusion of this measure in Germany is justified. The costliest measures of the ones that are currently applied in Germany are joint and strict liability for all damages. Our results further show that neighbours do not cause a problem and opportunities for reducing costs through agreements with them exist. Finally, we find that farmers’ attitudes towards GM crops affect the probability of adoption of Bt maize. Our results imply that strict liability will deter the cultivation of Bt maize in Germany unless liability issues can be addressed through other means, for example, through neighbours agreements.