结构性违约、信用分层与评级机构的策略性反应——来自中国信用债市场的证据

2014年以来，以主要集中于民企的"结构性违约"宣告了中国信用债市场刚性兑付的"结构性打破"，债券市场进入了新的发展阶段。利用2013-2017年债券数据，本文深入分析了结构性违约对评级机构行为和效率的影响，主要有如下发现：首先，信用评级的市场公信力会因政府隐性担保导致的"刚性兑付"而削弱；其次，结构性违约爆发之后，信用评级的整体效率有所提升，但在不同发行主体呈现分化，对于非城投类企业，信用评级对发行利差的影响显著增大，意味着评级公信力的显著提升，而对于城投类企业，评级效率并未明显改善；进一步研究表明，出现这种情况的原因在于评级机构在违约后采取了差异化的评级策略，对于违约风险较大的非城投类债券，评级机构倾向采取"收紧评级"的策略；对于违约风险较低的城投债，评级机构倾向于采取"放宽评级"的策略。这种策略性行为是导致市场"信用分层"的重要原因，并有可能推升民营企业的融资成本。     

复杂山区铁路客运站自动选址研究

无备选站址条件下的客运站自动选址是线站协同优化的前提和基础,而不局限于车站选址的代价最小化,同时考虑连接车站间区间线路的代价具有重要意义。构建复杂山区铁路客运站自动选址模型,首先,建立综合地理信息模型,基于线站一体化的设计理念,实现单个车站选址,确定站心位置及站坪方向;其次,以公路线形优化模型的改进算法完成站—站间自动选线设计;最后,将车站选址代价与区间线路代价紧密结合起来,计算综合代价,实现站址方案的优选。以山区铁路为例对该方法进行验证,结果表明,该方法能高效生成山区铁路车站方案集,并辅助设计人员进行方案优化。     

中国医疗保险体系中的自选择与医疗费用——基于灵活就业人员参保行为的研究

我国社会医疗保险已实现全覆盖,现阶段的主要问题在于医保基金能否实现可持续运行。在现行制度安排下,灵活就业群体参加城镇职工医疗保险可能存在逆选择问题,随着就业形态日趋多样化,这将加剧基金运行的不平衡。本文基于2012-2014年中国家庭追踪调查数据(CFPS),利用中国特有的制度特征,在实证上将逆选择效应同道德风险相区分,验证了选择参加城镇职工医保的人群是医疗费用较高的人群。估计表明,自愿选择参加城镇职工医保的人群医疗支出明显高于强制参保群体,大约高78%;而选择参加城镇职工医保的人群医疗支出比选择参加城乡居民医保高约45%。灵活就业人员参加城镇职工医保提升了他们的福利,但如何规避潜在的基金运行风险,是医保制度设计中不可忽视的问题。     

CAUSAL INFERENCE ON EDUCATION POLICIES: A SURVEY OF EMPIRICAL STUDIES USING PISA,TIMSS AND PIRLS

The identification of the causal effects of educational policies is the top priority in recent education economics literature. As a result, a shift can be observed in the strategies of empirical studies. They have moved from the use of standard multivariate statistical methods, which identify correlations or associations between variables only, to more complex econometric strategies, which can help to identify causal relationships. However, exogenous variations in databases have to be identified in order to apply causal inference techniques. This is a far from straightforward task. For this reason, this paper provides an extensive and comprehensive overview of the literature using quasi‐experimental techniques applied to three well‐known international large‐scale comparative assessments, such as PISA, PIRLS or TIMSS, over the period 2004–2016. In particular, we review empirical studies employing instrumental variables, regression discontinuity designs, difference in differences and propensity score matching to the above databases. Additionally, we provide a detailed summary of estimation strategies, issues treated and profitability in terms of the quality of publications to encourage further potential evaluations. The paper concludes with some operational recommendations for prospective researchers in the field.     

Relationship between city size and firm productivity – A new interpretation using the Chinese experience

This paper contributes to the literature on the relationship between city size and firm productivity by focusing on agglomeration, selection (market competition), and sorting (presence of firms with diverse productivity) effects using Chinese firm-level data for 1998–2013. Contrary to the existing literature, our parametric regression estimates from nearly two million firms show that when the selection effect is controlled, productivity advantage in big cities is reversed. This outcome is explained through a quantile regression showing the existence of left-sided sorting (inefficient firms sort themselves to larger cities) in big cities which is not captured in existing empirical literature. We further find that (1) left-sided sorting is stronger in exporters than non-exporters; (2) is also generated mainly in enterprises with high asset-liability ratios; and (3) selection has a positive effect on firm productivity, suggesting that market competition is key in an explanation of the rapid growth of big cities in China.     

Customizing calories: How rejecting (vs. selecting) ingredients leads to lower calorie estimation and unhealthier food choices

Customization of food products has increased substantially in recent years while the desire for healthiness and an emphasis on understanding and providing calorie information continues to dynamically change the landscape of restaurant retail. The authors report four studies demonstrating that different customization routes (i.e., rejecting alternatives from a full product offering versus adding alternatives to a basic product offering) lead to systematic, but predictable, differences in consumers’ estimations of calories. In particular, this research finds that a rejection (vs. selection) customization process leads consumers to persistently estimate lower calories in the final product, which then improves evaluations of the retailer and leads to unhealthier food choices. These findings occur when consumers estimate calories of the exact same final product using the different paths to customization as well as when they create their own customized final product, while accounting for differences in the quantity and type of ingredients selected, suggesting a very general difference in estimations. This research has important implications for consumers who want to manage their weight and for firms that need to manage consumers’ health perceptions.     

兰州铁路枢纽总图方案研究

合理确定兰州铁路枢纽布局有助于完善西北地区铁路网络,促进兰州—西宁城市群发展,提升欧亚大陆桥互联互通能力,发挥兰州地区的桥头堡作用。阐述兰州铁路枢纽现状,指出枢纽内客运站分工及货运设施功能存在问题,提出枢纽发展规划;研究提出兰州铁路枢纽总图方案,包括干支线、疏解线及联络线工程方案与总图方案设计。研究结果表明,兰州将形成衔接11条铁路干线,南客北货的大型环状枢纽格局,更好地支撑西北地区核心路网运输。     

Objective methods for graphical structural learning

Graphical models are used for expressing conditional independence relationships among variables by the means of graphs, whose structure is typically unknown and must be inferred by the data at hand. We propose a theoretically sound Objective Bayes procedure for graphical model selection. Our method is based on the Expected-Posterior Prior and on the Power-Expected-Posterior Prior. We use as input of the proposed methodology a default improper prior and suggest computationally efficient approximations of Bayes factors and posterior odds. In a variety of simulated scenarios with varying number of nodes and sample sizes, we show that our method is highly competitive with, or better than, current benchmarks. We also discuss an application to protein-signaling data, which wieldy confirms existing results in the scientific literature.     

基于快铁融合的上海铁路集装箱快运站选址研究

快铁融合可以充分发挥快递企业和铁路运输的优势,有效提升物流作业效率,达到运输资源分配平衡的效果,是多元化运输的发展方向。在既有和计划建设的铁路货运站中选择铁路集装箱快运站与快递企业集散网络衔接,以快递企业时间满意度和集散运输成本为目标,构建基于时间满意度的铁路集装箱快运站选址模型,以上海铁路集装箱快运站为例进行实证分析,提出保证铁路集装箱快运站与快递企业合理衔接的对策,为铁路集装箱运输融入快递市场提供决策支持,加速快铁融合的实施。     

石衡沧港城际铁路互联互通方案研究

突出功能定位,发挥路网互联互通作用,是高速铁路互联互通方案研究的关键。在阐述石衡沧港城际铁路互联互通现状的基础上,针对石衡沧港城际铁路客流特点和功能定位,分析石衡沧港城际铁路石家庄铁路枢纽、衡水铁路枢纽、沧州铁路枢纽和黄骅铁路枢纽等互联互通主要节点枢纽,通过衡水、沧州和黄骅铁路枢纽比选方案分析,提出石衡沧港城际铁路在通道中的枢纽方案,为区域连接线、城际铁路在方案互联互通作用提供研究支撑。