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.     

商业银行利率风险计量模型及实证分析--非平移收益曲线条件下的随机免疫策略

传统的久期理论建立在收益曲线平移等严格假设条件上，因而其在实践中的有效性大大降低了。根据Markowitz（1959）等理论可推导出：资产价格的总风险包括收益的方差和全久期向量两部分；假若商业银行采取现金中性（cash neutrality）的资产交易策略，风险计量模型可转换为线性规划问题，从而可以构建基于利率风险最小化模型的随机免疫策略。也就是说，引入随机免疫的理念来替代经典的免疫理论，通过实证分析得出：无现金交易条件下的随机免疫策略能够降低利率风险。     

最大持续产量原理在可持续发展实践中的应用

文章指出,实施可持续发展要以生态学原理为指导,其中较重要的就是最大持续产量原理。最大持续产量原理在农业、林业、渔业、有害生物防治、生物资源保护等方面有着广泛的应用。     

基于GARCH族模型对中国股市波动的分析与预测

运用GARCH类模型对沪深300指数序列的波动性、收益率进行了实证研究,并且对序列做了拟合与预测,获得了不错的效果。除此,还证实了中国股市存在着显著的非对称效应。     

The impact of fiscal positions on government bond yields in CEE countries

This paper investigates the influence of government debt and primary balance on long-term government bond yields in 10 Central and Eastern European (CEE) countries in the period 2000–2013. The results indicate that a one percentage point increase in the stock of government debt is associated with an increase in government bond yields of 2.7–4 basis points, while a one percentage point increase in the primary deficit to GDP ratio is associated with an increase in government bond yields of 12.9–24.3 basis points. We also find evidence of non-linearities in the debt-interest rate relationship, whereby the threshold after which the impact of debt turns from negative to positive is significantly lower than in advanced economies.     

短期生产决策理论下学生党支部最优规模分析

高校学生党支部是高校最重要的基层党组织团队之一。本文利用微观经济学短期生产决策理论,设置支部产出,构建数学模型,利用调查数据进行分析,对高校学生党支部这一特殊团队的规模最优进行了研究。     

A dynamic Nelson-Siegel yield curve model with Markov switching

This paper proposes a model to better capture persistent regime changes in the interest rates of the US term structure. While the previous literature on this matter proposes that regime changes in the term structure are due to persistent changes in the conditional mean and volatility of interest rates we find that changes in a single parameter that determines the factor loadings of the model better captures regime changes. We show that this model gives superior in-sample forecasting performance as compared to a baseline model and a volatility-switching model. In general, we find compelling evidence that the extracted factors from our term structure models are closely related with various economic variables. Furthermore, we investigate and find evidence that the effects of macroeconomic phenomena such as monetary policy, inflation expectations, and real economic activity differ according to the particular regime realized for the term structure. In particular, we identify the periods where monetary policy appears to have a greater effect on the yield curve, and the periods where inflation expectations seem to have a greater effect in yield determination. We also find convincing evidence of a relationship between the regimes estimated by the various switching models with economic activity and monetary policy.     

Some Potential Linkages for Input-Output Analysis with Flow-of-Funds

Three major, interrelated accounting statements, at the frontiers of quantitative economic analysis, are three interrelated systems, namely: (1) National income and product accounts (NIPA), (2) The input-output tableaux, (IO), and (3) flow-of- funds accounts (FF). The third-mentioned system is somewhat less available and used in only limited areas of macroeconomic analysis. This paper is mainly concerned with use of FF accounting systems. This system shows where financial resources originate, and where they go in support of real capital formation. In this respect, interest rates and other market-based financial rates are of key importance. While much macroeconomic analysis is based on the rates that fit the yield curve, showing the interest rate structure over various maturities of debt associated with a given degree of risk. In contrast, the FF accounts throw light on the whole spectrum of interest rates, across maturities and debt qualities. For example, in analysis of the real estate market and funding of capital formation there, it is important to have a full understanding of the course of mortgage rates of different maturities and qualities. In short, it is necessary to develop a full appreciation of supply and demand forces in the mortgage market, which often is not obviously related to movements of the operative rate for monetary policy, such as very short-term inter bank rates or call money rates. This paper attempts to provide material from the flow-of-funds accounts that would make it possible to analyze the movement of relevant mortgage rates or whatever other rates are needed to understand the financing of capital formation in real estate.     

Inventory inaccuracies in the wholesale supply chain

The inventory level shown in the Information System contrary to popular belief and assumptions in most academic papers and in spite of the considerable amounts invested in information technology, is often inaccurate. The inventory inaccuracy occurs when the inventory shown in the Information System is not in agreement with the actually available inventory. In this paper, we first describe the major factors generating inventory inaccuracy. Then, we provide situations permitting to manage an inventory system subject to errors. We provide a general framework permitting to model the inventory inaccuracy issue. In particular, we link the inaccuracy issue with the well known random yield problem. The shown link permits us to derive the optimal ordering policy of an inventory framework where demand satisfaction is done based on the inventory records (which are subject to inaccuracies). We also propose an analysis permitting to show the added value of an advanced identification system such as the RFID technology.     

黏土矿物对泥石流体屈服应力影响的实验研究

一般情况下,泥石流体屈服应力随着泥沙颗粒体积浓度的增大而增大,同时随着黏粒黏性的增强而增强。在此研究基础上,以泥石流体屈服应力为研究目标,选取了蒙脱石、伊利石、绿泥石、高岭土等4种常见的黏土矿物为研究对象,通过改变泥石流体中泥沙颗粒体积浓度、黏土矿物成分及黏粒重量百分含量得出:1一般情况下,黏土成份对泥石流体屈服应力影响的强弱关系依次为蒙脱石伊利石绿泥石高岭土。2泥沙颗粒体积浓度和黏粒百分含量对泥石流体屈服应力的影响呈指数关系。3综合分析泥沙颗粒体积浓度、黏土矿物成份、黏粒百分含量与屈服应力的关系后获得了黏土矿物下屈服应力的关系式。4用野外调查资料验证了上述泥石流屈服应力与泥沙颗粒体积浓度、黏土矿物的关系,具有一定的准确性。