基于ESDA-GWR的粮食单产及其驱动因子的空间异质性研究

在耕地面积扩展有限和城市化高速发展的背景下,粮食单产的区域差异对我国粮食安全具有重要意义。以我国31省（市、自治区）为研究单元,借助ESDA和GWR模型,结合我国各地自然条件的差异及其经济发展类型,揭示我国粮食单产的区域差异及其驱动因子的空间异质性。结果表明：1999—2008年,中西部地区粮食单产的增产对全国粮食产量的贡献越来越显著,75%的粮食单产增长潜力较大的区域集中在中西部;粮食单产存在着显著的空间相关性,各省域粮食生产重心发生移动,由传统的＂东部为主＂逐渐＂北上西进＂,向中西部地区欠发达省份集中;不同区域粮食单产的驱动因素呈现为一种非均衡联动的局域性特征,化肥施用量对粮食单产的影响在两个时间断面中差异最大,1999年回归系数全为正值,而在2006—2008年出现负值,这表明部分地区化肥对粮食单产的边际效应已经达到递减阶段。因此,应结合我国不同区域当前粮食单产的现状和驱动因子的效应机理,积极采取相应的有效措施以保障我国的粮食安全。     

复杂金融产品评数字化绩效评估

本文在分析范式上将复杂金融产品看成是关于其标的资产的或有要求权,复杂金融产品结构上本质差异在于其支付过程和边界条件。设计和构建一个统一分析框架,从风险和收益两个方面对复杂金融产品进行绩效评估,在方法和过程上采用数字模拟仿真技术实现。利用2007年度在国内市场公开发行的银行理财产品作为实证分析实例,评估结果表明国内市场理财产品基本符合风险收益平衡原则,但在产品发展和创新能力上,外资机构比中资银行具有优势。     

Return and volatility spillovers between currency and bond markets in India

This paper examines the return and volatility spillovers between the foreign exchange and bond markets of India using a bivariate asymmetric BEKK-GARCH (1,1) model for the period 4 April 2005 to 31 March 2017. We find the evidence of bidirectional return and volatility spillovers with asymmetric effects between these two markets. The spillovers are evidenced even during the periods when foreign portfolio investments in the Indian bond markets were relatively low suggests the existence of strong inter-linkages between both the markets.     

The impact of conservation tillage on maize yield and input demand: the case of smallholder farmers in north‐west Ethiopia

This study analyses the economics of conservation tillage (CT) with respect to its effect on maize yield and chemical fertiliser, herbicide, and female and male labour demand. We estimate production and input demand functions using seemingly unrelated regressions on plot‐level cross‐sectional farm household data collected in the north‐west of Ethiopia. A two‐step control function is applied to address potential endogeneity bias due to the inclusion of the CT adoption decision as an explanatory variable. Our results show that CT increases maize yield and chemical fertiliser demand. Additionally, the results show that the adoption of CT reduces female and male labour required for crop production. However, this is achieved through the increased use of herbicides, which might have an undesirable health and environmental effects.     

中国粳稻生产效率演变及区域差异

[目的]我国粳稻产量现阶段呈连续增长的态势,然而粳稻生产效率却存在无效率或波动剧烈的现象,研究我国的粳稻生产效率,有助于提升和稳定中国粳稻区域生产效率和水平从而间接保障我国粮食安全。[方法]使用超效率DEA方法测算中国13个粳稻生产省份的生产效率,分别从时间和区域上的差异进行分析。[结果]中国粳稻生产技术效率在时间趋势上逐渐趋于平稳,但是在2004—2007年间存在短暂的波动;在区域上主要是西南和东北粳稻生产区的技术效率水平较高,西北区在技术效率、纯技术效率与规模效率上都处于较低的水平;虽然河南、湖北、宁夏3个省份出现技术无效率,但规模报酬都处于递增的状态,仍有提升生产效率的潜力,应通过减少要素投入冗余来改变其无效率状态。[结论]粳稻生产技术无效率主要是由于种子费用、农药费用等生产要素的投入冗余造成的;若将来在保持纯技术效率和其他条件不变的情况下,通过提升规模效率水平会进一步提升我国粳稻的整体技术效率水平。基于上述分析有针对性地提出制定粳稻生产区域规划、发展适度规模经营、改善生产要素使用效率3方面的政策建议。     

Jumps in the convenience yield of crude oil

The potential presence of jumps and time-varying volatility in convenience yields can lead to abnormally fat tails, which has implications for investment in storage capacity, leasing and drilling for crude oil. In this paper we evaluate the potential for these features in convenience yields. To that end, we analyze the rate of change in convenience yields for five futures prices time horizons (1, 3-, 6-, 9- and 12-month ahead), allowing for the both jumps and time-varying volatility. We find that both features exert a statistically important effect on convenience yields, for each of the five time horizons. We also calculate the implied probability that at least one jump would occur on any date, which reveals a period of relative calm at the start of the fracking boom, when large stockpiles built up at the trading hub for West Texas Intermediate, and a period of considerable churn, after the ban on exporting crude oil was lifted. Both elements underscore a linkage between inventory holdings and convenience yields.     

A worldwide analysis of trend in crop yields and yield variability: Evidence from FAO data

The trend in crop yields and yield variability affects food security and impact agricultural and food policies. Recent studies in this area have either focused only on one country or performed global analysis on a handful of crops. We provide the first worldwide analysis of trend and variability for 8088 country-crop yield series taken from the FAO database, employing a robust estimator to cope with the adverse statistical effects of outliers. More than half of the series display a slowdown in yield growth due to a closing of the gap between realised and attainable yields as well as to agricultural policies promoting more sustainable agricultural practices. Around one fourth of the series show also an increase in yield variability as a consequence of climate change and changes in farm management practices. Yield variability is highest in Eastern Europe, Central Asia and Middle East and North Africa, where food security may be threatened.     

Government contracts and US bond yield spreads: A study on costs and benefits of materialized political connections

In a 1991–2013 sample of bonds issued by US public firms, we find that the cost of debt (yield spread relative to comparable Treasuries) of suppliers to government agencies is contingent on the strategic importance of the supplier's industry. The yield spreads for strategically unimportant government suppliers are higher than for firms that are not government suppliers. If government contracts serve as tangible evidence of political connections, these higher yield spreads indicate that weaker corporate governance as a cost of political connections outweighs the benefits of said connections. For the subsample of government suppliers from strategically important industries, where the benefits of implicit bailout guarantees and revenue stability outweigh the corporate governance problems, the cost of debt is lower than for firms that are not government suppliers. The higher (lower) cost of debt for strategically unimportant (strategically important) suppliers is confined to contracting with the federal government. Our findings are robust to alternative variable and sample specifications, and to endogeneity concerns.     

Effectiveness of harvest strategies in achieving multiple management objectives in a multispecies fishery

Fisheries management is characterised by multiple objectives, some of which may be complementary, while others may require trade‐offs between outcomes. Balancing these objectives is made more complex in the case of multispecies and multigear fisheries. In this paper, we develop a bioeconomic model that captures the key elements of such a fishery to test a range of potential harvest strategies to provide insights into how economic target reference points could lead to both desirable and undesirable management outcomes (e.g. discards). The model is developed as a long‐run optimisation model to identify target reference points to achieve multispecies maximum economic yield, and a dynamic recursive optimisation model, which includes more realistic representation of fishers’ behaviour, such as discards and trading of under‐caught species quotas. The potential economic, social and ecological impacts are evaluated using data envelopment analysis (DEA). The results suggest that the use of proxy target reference points can result in short‐term economic benefits at the cost of slower stock recovery and higher discarding. Limiting the number of species subject to quota controls may also prove beneficial in multispecies fisheries, while ensuring quota markets are efficient is likely to produce benefits irrespective of the harvest strategy adopted.