一种动态加权的LDPC译码方法

为了加快低密度奇偶校验（LDPC）码的译码速度，有效改善LDPC码的译码性能，针对校验节点更新过程中的对数似然比（LLR）值的大小，设计了一种LDPC码的动态加权译码方法。以IEEE 802.16e标准的奇偶校验矩阵为例，根据LLR值的变化规律，利用增长因子和抑制因子对和积译码算法和最小和译码算法进行动态加权。仿真结果显示，基于动态加权的译码方法相对于传统译码方法误码率都有明显改进，译码复杂度也有所降低。     

Solvency Ⅱ与C-ROSS非寿险保险风险最低资本要求比较研究——基于中国60家财产保险公司的经验证据

本文以非寿险业务保险风险最低资本要求为考察对象,研究了欧盟Solvency Ⅱ与中国C-ROSS的差异,并利用中国保险市场60家财险公司的经验数据,对两者之间的差异进行了实证和模拟分析。研究结果表明,Solvency Ⅱ和C-ROSS对中国财险公司保险风险最低资本要求存在差异。对于拥有传统业务结构的财险公司,Solvency Ⅱ对保险风险最低资本要求更高,但是这种差距随着公司业务规模的缩小而减弱;对于以经营某些专业险种为主的财险公司,主营业务险种对两者差异具有决定性影响。本文的研究结论详细解释了Solvency Ⅱ与C-ROSS在非寿险保险风险最低资本计算上的异同,对C-ROSS下一步的修订工作提供了一定的支持与参考。     

Forecast of realized covariance matrix based on asymptotic distribution of the LU decomposition with an application for balancing minimum variance portfolio

We derive the asymptotic distribution for the LU decomposition, that is, the Cholesky decomposition, of realized covariance matrix. Distributional properties are combined with an existing generalized heterogeneous autoregressive (GHAR) method for forecasting realized covariance matrix, which will be referred to as a generalized HARQ (GHARQ) method. An out-of-sample forecast comparison of a real data set shows that the proposed GHARQ method outperforms other existing methods in terms of optimizing the variances of portfolios.     

On the heterogeneous short‐term effects of minimum wages on labor demand

A strand of the literature documents no effects or even positive effects of a higher minimum wage on employment. This evidence is frequently linked to the existence of monopsonistic labor markets or search frictions. However, empirical studies show that these findings could be related to a low short‐term minimum wage–employment elasticity in a competitive labor market. We show that mixed theoretical employment effects of a minimum wage policy can be predicted in the short term in assignment economies with price‐taker agents and no search frictions.     

Cost Analysis of Calcium in Store Brand versus National Brand Grocery Products

Objective: This study was to determine if calcium fortification yields a higher price per serving in grocery store products. Researchers compared store brand to national brand grocery products in relation to cost in order to examine if calcium values were similar between store brand and national brand products. Methods: A total of 112 store brand and 211 national brand grocery products were collected from three low (national chain store), middle and high priced (Virginia and North Carolina regional store) grocery venues. Products were compared using price and calcium percentage per serving. ANOVA was used to determine between store brand and national brand for price per serving and calcium content, and between grocery venues. Results: National brand fortified products had a significantly lower mean price per serving when compared to national brand non-fortified products (p = 0.0002). There was no statistical difference between store brand fortified and non-fortified products (p = 0.9256). Low priced store brand products had the lowest mean price per serving ($0.34 ±0.24). Conclusions: This study found store brand products have similar calcium content as national brand products. Product cost was lower at low priced store compared to middle and high priced stores.     

最低工资标准、人力资本扩张与企业成本加成*

本文以人力资本扩张为切入点，构建了最低工资、人力资本扩张影响企业成本加成的理论框架，并使用中国1998-2013年284个地级市的工业企业数据进行了经验研究。结论显示：最低工资上调会显著抑制企业成本加成的提升，削弱了企业的市场势力，但该抑制效应在人力资本扩张的背景下得以缓解。同时本文通过进一步分组回归发现，最低工资标准与人力资本扩张对企业成本加成具有明显的异质性影响。因此，适度、稳定调整最低工资标准及推动人力资本质量的整体提升有助于保持企业成本加成能力及其动态竞争力。     

四川省水稻产投特征变迁及技术进步对单产的影响

[目的]了解四川水稻产投特征和技术进步对单产的影响,促进水稻可持续生产。[方法]分析了改革开放以来四川省水稻产投特征和技术特征变动,并基于索洛余值法测算了1980~2015年四川省科技进步对水稻单产的贡献情况。[结果](1)全省水稻单产水平及物质与服务费用投入均呈现波动增长趋势,人工投入逐年递减,但人工成本在生产成本中的比重较大;(2)四川省水稻品种选育、栽培管理技术、推广技术、稻作经营方式和农业政策不断变迁,更适应当前以普通家庭生产和新型经营主体共同发展的局面对技术的需求;(3)整体来看,近36年技术进步对四川省水稻单产水平提高的贡献率较低,生产经营较为粗放;(4)分时期看,2005年前,技术进步对全省水稻单产水平提高的贡献率较高,但之后尤其是近5年,技术进步并未对水稻单产水平提高产生影响,要素投入是水稻单产水平提升的主要因素。[结论]提出了加强科技研发及投入水平、"一主多元"联合推广、生产管理技术培训和丘区节本增效生产的政策建议。     

Financial Insecurity in a World of Plenty

Abstract

The U.S. economy is addicted to the simulative impacts of household borrowing. Household debt has grown dramatically since the 1990s and has served to mitigate the detrimental effects of stagnant household wages. The accumulation of this debt has also had the macroeconomic impact of stimulating the economy, pushing it closer towards full employment. However does full employment stimulated by household indebtedness actually represent economic progress? It is argued that even the poorest citizen in a modern industrialized society is better off than a king of feudal Europe, yet in the United States such material prosperity is often tied to social insecurity thanks to debt. The growth of this debt has been enabled by a financial system that has evolved dramatically over the past forty years. The U.S. financial system’s primary role is no longer to finance investment but is rather a tool that enables a separation of ownership from use. Debt has fueled corporate profits which have enriched the shareholding class while at the same time the system has reduced the financial security of the majority of workers. This article crystalizes these issues by analyzing the differentials in financial circumstances faced by workers and shareholders in several major U.S. firms.     

Does trade size restriction affect trading behavior? Evidence from Indian single stock futures market

Algorithmic traders use their advantage of speed to execute a large number of small-sized trades in a very short time. In the presence of a minimum trading unit (MTU) restriction, they are forced to trade at the smallest possible sizes, often restricted by the MTU. Using a novel data set of single stock futures market obtained from the National Stock Exchange of India, we show that the MTU restriction acts as a binding constraint for traders while optimizing trade sizes. Contrary to expectation, we find weak evidence that liquidity is positively impacted by the contract size revision.     

Risk measures for variable annuities: A hermite series expansion approach

In this study, we propose an efficient approach to the calculation of risk measures for an insurer's liability from writing a variable annuity with guaranteed benefits. Our approach is based on a novel application of the Hermite series expansions on the transition density of a diffusion process to the insurance setting. We compare our method with existing methods in the literature, including the analytical method, spectral method and Green's function method, and illustrate its substantial advantages in calculating risk measures for variable annuities with different guarantee structures. The improved efficiency makes our method flexible to practical implementation in reporting risk measures on a daily basis. We also conduct a sensitivity analysis of the risk measures with respect to key parameters.