新冠肺炎疫情对全球食物安全的影响及对策

当前,新冠肺炎疫情已在全球扩散,许多本就因为冲突、自然灾害或气候变化而深陷食物不安全的国家和地区的防疫形势也日益严峻。虽然目前全球食物供给总体充足,食物价格稳定,但疫情的快速蔓延将给全球食物安全带来威胁。由于隔离和边境关闭,市场、供应链和贸易受到波及,全球食物的供给受到影响。食物流通渠道可能因运输中断和更加严格的检疫措施而受阻,运输成本和贸易成本增加、效率降低。一些国家为保障国内食物供应而采取限制出口的行为,将影响依赖于粮食进口的国家进口粮食,也不利于依赖于出口初级农产品的低收入发展中国家出口农产品。封锁措施带来的经济影响使居民收入和购买力下降,居民获得充足的营养食物变得更加困难。食物安全不再是一个区域性问题,而是一个需要共同应对的全球性问题,各国应当共同努力,加强合作和全球治理,对最弱势群体采取迅速的保护和援助措施。既要确保国内食物供应链的正常运行,同时,应该保持贸易开放,并利用和创新电子商务保障食物供应,保障全球粮食安全。     

新冠肺炎疫情对我国粮食安全的影响分析及稳定产量的建议

稳定粮食安全根基是应对各类黑天鹅、灰犀牛事件的有力保障。疫情期间,充足的粮食供给再次发挥了安天下、稳民心的作用。从目前调查的情况来看,疫情对粮食生产经营的影响是暂时的、局部的、有限的,疫情持续也带来农资价格上涨、物资到位迟缓等问题。但种粮效益低、农业气象偏差、传统病虫害与输入性虫害叠加、国际经贸形势日趋复杂等挑战交织,是确保全年粮食产量、供应稳定的主要挑战。要高度重视抗疫战线拉长带来的负面影响,积极疏通农资供应渠道、有序组织返田返工,更要稳住政策支持,完善设施装备配套,强化技术支撑,做好防灾减灾。     

我国物流业2020年发展回顾与2021年展望

2020年是我国全面建成小康社会决胜之年和“十三五”规划收官之年。这一年,面对新冠肺炎疫情严重冲击与复杂国际形势严峻挑战,我国物流业统筹推进抗击疫情和现代物流体系建设工作,在为抗疫保供、复工复产做出重要贡献的同时,取得了来之不易的不俗成绩。但与此同时,物流业发展不平衡不充分不协调问题依然存在,物流业整体发展水平与应对不确定因素的能力有待提高,国际物流、应急物流、绿色物流等方面尚有短板,运行规模与质量方面“大而不强”,与人民群众日益增长的美好生活需要和经济高质量发展的要求还存在一定差距,物流大国向物流强国的转变任重道远。2021年既是“十四五”规划的开局之年,也是全面建设社会主义现代化国家新征程的起步之年。未来一段时期,我国经济长期向好的基本面不会改变,物流业平稳增长的态势不会改变,需要我们在精准把握新发展阶段特点、认真贯彻新发展理念、支撑构建“双循环”新发展格局、明确现代物流发展新方位的基础上,以构建现代物流体系、建设物流强国为目标,以推动高质量发展为主题,以供给侧结构性改革为主线,认真谋划“十四五”乃至2035年发展战略,高瞻远瞩把握行业趋势,脚踏实地做好当前工作,确保开好局,起好步。具体而言,一要保障产业链供应链自主可控、安全高效;二要做强扩大内需战略支点;三要推进物流业制造业深度融合;四要加速物流数字化转型;五要完善物流基础设施网络;六要助力更高水平对外开放;七要挖掘区域协同发展潜力;八要补齐“三农”物流短板;九要实现物流绿色可持续发展;十要不断优化营商环境。     

The Effects of Cannabis Use on Wages of Prime‐age Males*

This paper uses a data set collected among inhabitants of Amsterdam, to study whether wages of prime‐age male workers are affected by cannabis use. The analysis shows that recent cannabis use has a negative effect on wages. The size of the wage effect depends on the age of onset. The earlier the start of cannabis use the larger the negative wage impact.     

Feedback and the success of irrational investors

We provide a model in which irrational investors trade based upon considerations that have no inherent connection to fundamentals. However, trading activity affects market prices, and because of feedback from security prices to cash flows, the irrational trades influence underlying cash flows. As a result, irrational investors can, in some situations, earn abnormal (i.e., risk-adjusted) profits that can exceed the abnormal profits of rational informed investors. Although the trading of irrational investors cause prices to deviate from fundamental values, stock prices follow a random walk.     

英国中产阶级与19世纪城市发展

19世纪英国城市的迅速发展,促进了城市社会中新型中间阶层的不断发展壮大,预示了英国社会由两极型社会向着橄榄型社会演变的趋向。而中产阶级的茁壮成长,反过来又对城市的发展产生了巨大的影响。它促使城市功能形态发生变化,出现工业区、商业区、居住区的功能分区。从交通方式到居民居住模式都发生了变化,中产阶层及社会精英迁居城郊或郊区的独立、半独立式住宅,使城市发展出现了郊区化趋势。此外,中产阶级的壮大,还促进了城镇管理走向民主,从城镇寡头统治向选举产生的市政机关演变。     

On the use of profit data to estimate the social cost of monopoly power in an oligopoly

Relatively high estimates of the welfare cost of monopoly power in U.S. manufacturing industries have been obtained by economists who use the Lerner equation to estimate this welfare cost from profit data. These Lerner equation loss estimates are appropriate for a monopoly with constant costs and linear demand. But if the industry is an oligopoly in a Nash-Cournot equilibrium, the Lerner equation loss estimates can be more than twice as large as the actual welfare gain that would result from the elimination of monopoly power. Partial and general equilibrium examples are presented to illustrate the nature of these estimation errors.     

新冠肺炎疫情的经济影响分析：长期视角与短期应对*

本文从需求和供给两侧分析了此次新冠疫情对我国经济的短期和长期影响。在需求侧，基于理论分析和非典疫情对经济的影响特征，经济总需求会随着此次疫情的结束而在短期内快速得到恢复。但此次疫情也会加大总需求和居民收入增速的下行压力。在供给侧，疫情不仅会降低劳动力资源配置效率，加剧劳动力供需结构矛盾，同时也大幅降低了我国的资本投资，在缺乏有效干预措施下，很可能加剧我国资本投资和经济总体增速的短期下滑趋势。而基于理论分析，相应供给冲击也将对我国长期产出带来增长压力。基于疫情对我国经济需求侧和供给侧的影响分析，2020年要实现全面建成小康社会的经济目标需要实施改革力度更大、更为有效的财政和货币等支持政策。     

Farmers’ Willingness to Pay for a Tuberculosis Cattle Vaccine

We use contingent valuation (CV) and choice experiment (CE) methods to assess cattle farmers’ attitudes to and willingness to pay (WTP) for a bovine tuberculosis (bTB) cattle vaccine, to help inform vaccine development and policy. A survey questionnaire was administered by means of telephone interviews to a stratified sample of 300 cattle farmers in annually bTB‐tested areas in England and Wales. Farmers felt that bTB was a major risk for the cattle industry and that there was a high risk of their cattle getting the disease. The CE estimate produced a mean WTP of £35 per animal per single dose for a vaccine that is 90% effective at reducing the risk of a bTB breakdown and an estimated £55 for such a vaccine backed by 100% insurance of loss if a breakdown should occur. The CV estimate produced a mean WTP of nearly £17 per dose/per animal/per year for a vaccine (including 100% insurance) which, given the average lifespan of cattle, is comparable to the CE estimate. These WTP estimates are substantially higher than the expected cost of a vaccine which suggests that farmers in high risk bTB ‘hotspot’ areas perceive a substantial net benefit from buying the vaccine.