Classical Swine Fever Changes the Way Farmers Value Pigs in South Africa

Although there is growing demand for animal products in Africa, production is stagnating. Appropriate management of livestock diversity could help reinvigorate production, contribute to food security and improve farmers’ livelihoods, particularly in subsistence‐oriented systems. We assess differences in farmers’ preferences and economic values for pig traits across different production systems and across areas that have been affected and unaffected by classical swine fever (CSF). Not surprisingly, market‐oriented farmers derived higher values from the productive traits such as heavy slaughter weight and large litter size found in exotic pig genotypes. Subsistence‐oriented farmers, particularly in swine fever affected areas, placed high value on tolerance to disease. We found that CSF changed farmers’ preferences for adaptive traits, and less so for productive traits. Therefore, indigenous breeds become more valuable for subsistence farmers and crossbreeds for market‐oriented farmers if CSF is a risk. Our results can have implications for breeding and conservation strategies and for compensation strategies after culling, and will become increasingly relevant if, as predicted, heat waves and disease outbreaks become more frequent in pig production systems in South Africa with climate change.     

商业银行效率研究：文献综述及建议

本文阐述了国内外研究者对商业银行效率的理解,笔者对衡量银行效率所采用的非参数法和参数法进行了详细的说明,并比较了各方法的优缺点。同时详细分析了银行效率函数中投入和产出的界定,及其他影响银行效率的因素,重点综述了产权制度和外资银行引入水平对本国银行效率的影响。最后,本文对效率前沿函数法和研究银行效率的目的提出了自己的理解。     

内蒙古人口结构、收入增长与城镇居民储蓄率的实证研究

从历年反映人口结构的相关数据中,发现内蒙古的人口结构在逐渐变化,劳动人口对未成年人口的抚养比率逐渐降低,对老年人口的抚养比率却逐渐提高。内蒙古人口年龄结构类型逐步进入老年型,而人口老龄化势必会对居民储蓄率产生一定的影响。本文选取了1985-2012年的相关变量数据,通过建立向量自回归模型及协整检验、脉冲响应函数和方差分析等一系列针对非平稳时间序列建模的分析方法,在一定的经济理论基础之上,分析了人口结构、收入增长对内蒙古居民储蓄率的影响。本文在人口结构、收入增长与居民储蓄率的实证分析中,首先验证了凯恩斯的绝对收入理论,不考虑人口结构的改变,得出影响储蓄率的主要因素并不是收入,也说明凯恩斯的绝对收入理论并不能很好的解释内蒙古当期的储蓄现象。然后又以莫迪利安尼的生命周期假说为理论基础建模,得出的结论与生命周期假说一致。人口老龄化会导致储蓄率的下降,而且人口结构的变化对储蓄率的影响远大于收入。长期来看,由储蓄率、收入增长率、负担少儿系数和负担老年系数这四个变量构成的经济系统是稳定的。     

Trade Openness and Exchange Rate Regimes

The paper evaluates the net welfare gains of inflation targeting over a fixed exchange rate as a function of a country's trade openness, using a multisectoral structural model calibrated to Chile. For most calibrations with separable preferences, net welfare gains are increasing in trade openness. The reason is that in more open economies terms of trade shocks, which favor inflation targeting, become quantitatively more important, while price markup shocks in the imperfectly competitive nontradables sector, which favor exchange rate targeting, become less important. The most important exception is heavily indebted countries, where net welfare gains are decreasing in trade openness.     

Common Institutional Ownership and Earnings Management*

This study examines the relation between earnings management and block ownership of same‐industry peer firms by a common set of institutional investors (common institutional ownership). This relation is important given the tremendous growth of common institutional ownership and the significant influence of blockholders on financial reporting. We hypothesize that common institutional ownership mitigates earnings management by enhancing institutions' monitoring efficiency and by encouraging institutions to internalize the negative externality of a firm's earnings management on peer firms' investments. Consistent with our hypothesis, we find that higher common institutional ownership is related to less earnings management. Analyses of a quasi‐natural experiment based on financial institution mergers show that this negative relation is unlikely to be driven by the endogeneity of common institutional ownership. Cross‐sectional tests provide evidence that the negative relation is stronger among firms for which common institutional ownership is likely to generate a greater reduction in institutions' information acquisition and processing costs, and among firms whose severe financial misstatements are more likely to distort co‐owned peer firms' investments, supporting both mechanisms underlying our hypothesis. Our findings inform the ongoing debate on the costs and benefits of common institutional ownership by highlighting an important benefit: the enhanced monitoring of financial reporting.     

中国半导体行业发展影响因素的实证研究——基于柯布-道格拉斯生产函数的回归分析

半导体行业作为自主可控领域的核心基础产业,是国家的战略性、先导性产业.中国需要抓住时机,推动半导体产业的进一步发展.收集了2014—2019年中国半导体产业的相关数据,以柯布-道格拉斯生产函数为基础,选定4个影响因素建立回归模型,对模型进行检验和修正.经过分析得出,影响中国半导体产业发展的关键因素是研发投入和产业集聚度,中国应该主要从这两方面发力,推动半导体行业的发展.     

辅助方程法解的推广及其非线性发展方程的精确孤立波解

本文将辅助方程法中的解的展式取为更一般的形式进而推广辅助方程法并利用此推广给出（1＋1）维组合KdV方程和（1＋1）维mKdV方程的精确孤立波解.     

The impact of decoupled subsidies on productivity in agriculture: a cross‐country analysis using microdata

The decoupling of direct payments from production introduced in the reform of the Common Agricultural Policy is expected to make production decisions more market‐oriented and farmers more productive. However, ex‐post analyses of the productivity of farms have yet to uncover any evidence of a positive impact of the decoupling policy on farm productivity. Using Irish, Danish, and Dutch farm‐level data, we identify whether the decoupling policy has contributed to productivity growth in agriculture and farm product adjustment behavior. We find some evidence that the decoupling policy had significant positive effects on farm productivity and behavioral changes related to farm specialization.     

基于小波神经网络的鱼类价格预测研究

鱼类市场价格是影响渔民收益的重要因素,因此如何能够准确分析和预测鱼类的价格是一个十分重要的问题.论文在考虑了BP网络原形的一些缺点和不足,尝试在传统BP算法的基础上将网络神经元中的激励函数换成小波子函数,组建成的小波神经网络.通过对鲈鱼价格的预测,验证了小波神经网络的可行性,然后基于阿里巴巴的鲈鱼价格的历史数据,验证了该方法的合理性.最后开展对新疆乌伦古湖水产综合基地三类主要鱼类价格预测的实证研究,研究结果表明河鲈和梭鲈的价格会有小幅的波动,但高白鲑的价格会有大幅的提升.因此,小波神经网络作为一种传统神经网络的改进,可用于预测鱼类价格的短期预测,为水产基地的决策提供依据.     

基于粗糙集的四川省能源可持续发展灰色评估

针对我国能源结构可持续发展评估过程中存在的指标冗余、权重确定主观性较强以及信息不确定等问题,构建基于粗糙集的能源可持续发展灰色评估模型进行合理科学评估。以四川省实际数据为样本,对初步选取的指标进行约简,并利用粗糙集理论中属性重要性对指标进行度量确定权重,最后采用灰色聚类理论中白化权函数构建的可持续发展评估模型进行评估。评估结果显示,四川省能源、环境系统呈现出强可持续发展态势,而经济系统表现为弱可持续性。