基于SFA模型的河南省粮食产量时空变化及投入要素影响

[目的]粮食问题影响着一个国家的国民经济发展和人民生产、生活,农业在整个社会生产活动中占有重要地位,河南省是全国农业大省,对河南省粮食产量进行分析具有重要的现实意义。[方法]以2005—2015年河南省各县粮食产量和投入要素为研究对象,将研究数据面板化,利用线性相关、随机前沿生产函数模型、脱钩分析等方法,运用ArcGIS 10.1、Eviews 8.0和SPSS 19.0等软件,对河南省各县粮食产量时空变化、投入要素影响程度和脱钩效应进行分析。[结果]模型运算结果表明文章选用模型效果较好,能够反映粮食产量的时空变化以及其与投入要素之间的关系,且符合河南省粮食产量实际情况。研究结果表明:(1)从时间上来看, 2005—2015年河南省粮食产量总体呈线性上升趋势;(2)从空间上来看,河南省中部、北部、东部和南部粮食产量较高,西部受地势因素影响粮食产量较低;(3)粮食产量与化肥施用折纯量、粮食播种面积、农民经营性收入、农药施用量、农业机械总动力和乡村农业人口呈正相关关系,与农村用电量呈负相关关系;(4)化肥施用折纯量、农村用电量、农药施用量存在脱钩效应,粮食播种面积、农民经营性收入、农业机械总动力不存在脱钩效应。[结论]应保持目前粮食播种面积不变,提高农业机械总动力,突出投入要素的影响,同时对河南省各县进行区域功能定位。     

Evaluating the impact of land fragmentation on the cost of agricultural operation in the southwest mountainous areas of China

Given the background of the increasing opportunity cost of farming and the popularization of labour-saving technology, increased fragmentation has gradually become a key factor in the devaluation and abandonment of land assets. To systematically identify the costs of fragmentation, we use a series of indicators such as the number of plots, the Simpson index, the plot-homestead distance and the total minimum commuting time from the homestead to all plots to measure the extent of fragmentation. A translogcost function is developed and estimated using survey data from three periods, 2011, 2014 and 2017; the data include an effective sample of 1064 household-year observations involving 6599 plot-year observations in Chongqing, China. The extent of fragmentation in the mountains of southwest China is quite serious compared with that in other countries and regions. The Simpson index is 0.63, and on average, 6.06 mu (1 mu = 666.67 m² or 1 mu = 1/15 ha) of cultivated land is distributed in 6.16 plots, while the total minimum commuting time from the homestead to all plots is approximately 45 min. An increase of one standard deviation in the number of plots, the Simpson index or total minimum commuting time would lead to cost increases of 7.1 %, 15.1 % and 12.2 %, respectively, if other conditions remain unchanged. The channel for the above result involves the changes in the cost share of inputs caused by fragmentation, which increase the labour cost share and reduce the machinery cost share. There is an inverted U-shaped relationship between farm scale and production cost with an inflection point at 47 mu; that is, costs begin to decrease when the scale exceeds 47 mu. However, the average farm scale is currently only 6.06 mu. In addition, production costs can be significantly reduced by renting-in land and implementing land consolidation. To reduce land system-induced costs in mountainous areas, the government should rationally consolidate land to achieve moderate-scale management, reduce the transaction costs of land transfers and popularize machinery suitable for complex terrain.     

国有林场贫困测定与差异性研究

基于2008—2017年国家林业局对中国28个省(市、区)国有林场的调研数据,运用等价性检验的方法从地理位置、经济状况、可持续经营和发展能力层面上对国有林场的贫困测度和差异性进行实证分析。研究结果表明:国有贫困林场不一定位于贫困县,并且与国有非贫困林场之间的差异逐渐缩小;国有贫困林场区域异质性强,经济发展水平较低;国有贫困林场在森林资源基础、人力资源基础、基础设施和生产条件等方面的可持续发展能力较差。因此,提出了相关林业部门应该鼓励国有贫困林场发展特色林产品;加大扶贫资金投入;改善职工生计条件;加强资金管理意识等政策建议。     

长江经济带农业绿色生产效率及其时空分异特征研究

［目的］从静态分析和动态分析两个方面，阐释长江经济带农业绿色生产效率和农业绿色全要素生产率的时空分异特征以及生产率增长来源，以期为提高长江经济带农业绿色发展质量提供科学决策依据。［方法］文章基于资源环境约束的角度，利用MinDS模型和Global Malmquist Luenberger指数相结合的方法，测算长江经济带农业绿色生产效率和农业绿色全要素生产率，并将农业全要素生产率变化分解为纯技术效率变化（PEC）、纯技术变化（PTC）、规模效率变化（SEEC）和规模技术变化（SETC）4个部分。［结果］（1）长江经济带农业绿色生产效率水平较高，且呈不断增长趋势，下游地区的农业绿色生产效率高于中、上游，且中、上游与下游地区的差距不断拉大； （2）长江经济带农业绿色全要素生产率增长较快，以3年为1个周期，呈现波动式上升趋势，其增长主要源于纯技术进步和规模技术提高； （3）长江经济带下游农业绿色全要素生产率增长率最高，上游次之，中游最低，其中，下游农业绿色全要素生产率增长主要源于纯技术进步，中游是纯技术效率改进、纯技术进步和规模技术提高共同作用的结果，上游则源于纯技术效率改进、纯技术进步和规模效率提高。［结论］长江经济带上、中、下游三大区域的农业绿色发展水平和发展能力存在较大差异，需制定差异化政策，以调整农业增长模式，促进农业转型升级，实现高质量发展。     

我国蛋鸡养殖环境全要素生产率测度及省域比较分析

［目的］蛋鸡养殖场规模化养殖与生态环境保护协调发展问题是蛋鸡养殖业可持续发展过程中面临的关键性问题，测度我国大、中、小3种规模下不同省份蛋鸡养殖场的环境全要素生产率，并从时间、地区两个维度对蛋鸡养殖场的环境全要素生产率进行比较。［方法］利用2004—2016年不同养殖规模蛋鸡养殖场的投入和产出数据，文章基于SBM函数的Malmquist Luengerber（ML）指数方法，对蛋鸡养殖场环境全要素生产率进行分解，将其分解为技术进步指数、效率改进指数。［结果］（1）蛋鸡养殖场环境全要素生产率整体呈现下降趋势，同时与蛋鸡养殖规模呈反比，蛋鸡养殖场规模越大，蛋鸡养殖环境生产率越小。（2）蛋鸡养殖场效率存在效率改善，但养殖技术进步率相对较低，尤其是对小规模养殖场而言，改善空间更明显； （3）蛋鸡养殖环境全要素生产率区域差异较为明显，整体来看，蛋鸡养殖主产区环境全要素生产率高于非主产区。［结论］加强蛋鸡产业科技创新水平以及公共服务设施的投入，提高养殖户的废弃物无害化处理能力，推行蛋鸡养殖的规模化和标准化发展，进一步改善养殖效率，以促进蛋鸡养殖规模化和生态环境保护协调发展。     

Systemic financial risk early warning of financial market in China using Attention-LSTM model

We propose an Attention-LSTM neural network model to study the systemic risk early warning of China. Based on text mining, the network public opinion index is constructed and used as a training set to be incorporated into the early warning model to test the early warning effect. The results show that: (i) the network public opinion is the non-linear Granger causality of systemic risk. (ii) The Attention-LSTM neural network has strong generalization ability. Early warning effects have been significantly improved. (iii) Compared with the BP neural network model, the SVR model and the ARIMA model, the LSTM neural network early warning model has a higher accuracy rate, and its average prediction accuracy for systemic risk indicators has been improved over short, medium and long terms. When the attention mechanism is included in the LSTM, the Attention-LSTM neural network model is even more accurate in all the cases.     

广西农业生态脆弱性评价及区划研究

［目的］随着经济的快速发展，我国各地区都面临着不同程度的农业生态脆弱性，通过研究特殊地形和气候下的农业生态脆弱性，有助于为农业生态环境的综合治理提供参考。［方法］文章以广西为例，通过构建评价指标体系，采用层次分析法和熵权法确定综合权重，通过构建综合评价模型对广西农业生态脆弱性程度进行评价，利用ArcGIS对生态脆弱性进行分级，以期探究广西农业生态脆弱性的空间分布情况。［结果］权重分析结果表明水蚀面积的权重值最高为0134，年平均降水量的权重值为0113，自然环境指标相对于农业生产和经济指标对农业生态脆弱性的影响更大。区划研究结果表明广西农业生态脆弱性区域大致可分为5个区域，分别是桂西峰丛洼地带、桂东山地丘陵地带、桂中低山丘陵地带、桂东北山地、桂南沿海丘陵地带。［结论］广西农业生态环境整体来看较为脆弱，处于轻度和中度脆弱等级，但生态环境问题仍不容忽视。为了改善农业生态脆弱性，政府应实行区域的联合防治，加大对农业生态环境的监督和治理，积极探寻生态、环保的农业发展方式，调整产业结构，改善农业生态环境的状态，促进广西农业的可持续发展。     

An information-theoretic approach for forecasting interval-valued SP500 daily returns

We develop an iterative and efficient information-theoretic estimator for forecasting interval-valued data, and use our estimator to forecast the SP500 returns up to five days ahead using moving windows. Our forecasts are based on 13 years of data. We show that our estimator is superior to its competitors under all of the common criteria that are used to evaluate forecasts of interval data. Our approach differs from other methods that are used to forecast interval data in two major ways. First, rather than applying the more traditional methods that use only certain moments of the intervals in the estimation process, our estimator uses the complete sample information. Second, our method simultaneously selects the model (or models) and infers the model’s parameters. It is an iterative approach that imposes minimal structure and statistical assumptions.     

Towards the Development of a Tax System Complexity Index

Reducing tax system complexity is a common goal amongst policymakers; yet there is no commonly agreed definition of complexity. This paper seeks to fill this gap, by proposing the construction of an index of tax system complexity, conceived as a summary indicator of the overall complexity of a tax system at a particular point in time. If adopted, such an index would not only enable assessment of the changing level of a country's tax system complexity over time, but may also facilitate comparisons of the relative complexity of different countries' tax systems in future.     

Diversification and sophistication of livestock products: The case of African countries

This study assesses the level of sophistication of livestock products in Africa by evaluating technology intensity and economic complexity of each product. Using trade data from 1995 to 2012, livestock commodity exports are classified based on technology intensity. Employing a method of reflection in computing the economic complexity of export products, we find that one fifth of African livestock commodity exports are manufactured with low technology while the rest is composed of raw materials. The results also show that the ten most complex livestock commodities represent about a third of African livestock total exports while the world level is almost double this figure. Yet African countries spend a huge share of their wealth on importing complex products. The results imply that by exporting non-complex products Africa loses nearly a third of the total value of its livestock exports. To boost the value of livestock products, African countries should exploit their untapped potential while securing the domestic market to achieve import substitution. This can be done by integrating with global value chains or developing niche markets at the regional or international markets and improving productive capabilities.