SELECTION BIAS CORRECTIONS BASED ON THE MULTINOMIAL LOGIT MODEL: MONTE CARLO COMPARISONS

Abstract.  This survey presents the set of methods available in the literature on selection bias correction, when selection is specified as a multinomial logit model. It contrasts the underlying assumptions made by the different methods and shows results from a set of Monte Carlo experiments. We find that, in many cases, the approach initiated by Dubin and MacFadden (1984) as well as the semi-parametric alternative recently proposed by Dahl (2002) are to be preferred to the most commonly used Lee (1983) method. We also find that a restriction imposed in the original Dubin and MacFadden paper can be waived to achieve more robust estimators. Monte Carlo experiments also show that selection bias correction based on the multinomial logit model can provide fairly good correction for the outcome equation, even when the IIA hypothesis is violated.     

建筑市场信息不对称及治理对策研究

本文基于不对称信息理论,建立了委托代理关系下的建筑业信息模型,并具体分析了建筑业目前由于信息不对称造成的各种问题,最后对相关问题提出了几点治理对策和建议。     

城市群协调发展评价理论与方法研究

论文在梳理文献的基础上建立了城市群协调发展的PREES系统模型,并构建城市群人口、资源、经济、环境、社会系统发展水平的综合评价指标体系,借助于主成分分析法构建了城市群协调发展程度的评价模型,然后针对陕西关中城市群发展现状进行案例研究,在测度关中城市群内部各子系统发展水平的基础上评价关中城市群1990年至2005年的协调发展程度,并就关中城市群的未来协调发展提出若干政策建议.     

工业园区绿色招商指标评价体系研究

本文分析了目前国内招商引资中出现的问题，提出了综合考虑投资环境和扫商要求的工业园区绿色招商及其评价指标体系，给出了相应的评价方法、同时对苏州工业围区的绿色招商水平作了具体评价。     

Wheat variety yield data: Do commercial and public performance tests provide the same information?

Wheat yields from reported performance test results are of economic importance to wheat producers, since their profits depend on selecting the optimal variety for their location. However, our data shows differences in absolute and relative wheat yields between commercial and public wheat breeding program's performance test data in Kansas. Newly available data are used to test if the difference in yields arose from potential selectivity bias, and to determine the contribution of private and public wheat breeding programs to varietal yield improvement during 2007–2012. Both Heckman selection models and multiple regression showed no statistical evidence of the potential presence of selectivity bias rather, managerial practices, agronomic conditions, field location, and inherent genetic traits of the seed variety were identify as the source of yield differences.     

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.     

Assessing self-selection and endogeneity issues in the relation between activity-based costing and performance

Studies investigating the relation between ABC adoption and performance are inconclusive and plagued with econometric problems. This study extends prior research to investigate the association between ABC adoption and four manufacturing plant performance measures (cycle-time improvement, quality improvement, cost improvement, and profitability) and to assess selection bias and the endogenous nature of their relationship. I use the Heckman (1979) model to assess sample selection bias and the Wooldridge (2002) 2SLS-IV approach, to investigate endogeneity. After controlling for sample selection bias and endogeneity, the coefficient of ABC under the Heckman method and ABC_fit under the 2SLS-IV method becomes significantly higher compared to the coefficient of ABC under the OLS method. In addition, both the inverse Mills ratio, under the Heckman model, and Hausman F-test, under the Wooldridge 2SLS approach, are positive and significant, confirming the presence of both sample selection bias and endogeneity. Overall, I find that controlling for sample selection bias and endogeneity is essential in properly assessing the significance of ABC-performance association.     

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.     

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。     

Why do some consumers shop in this pharmacy? A cross-check of vulnerable characteristics and store types

Research on vulnerable consumers remains unfailing in macromarketing and social marketing. Yet it is unclear how to operationalize the vulnerable consumers by demographics and further to this it is rarely touched how the vulnerable consumers defined by different measures make decision when choosing the place to shop especially in pharmacy retailing sector. The authors conduct a comparative study of variously-defined vulnerable consumers for their shopping store types in an urban Chinese city to investigate how people with distinct backgrounds develop their decision making rules and choose different types of retail pharmacies. This paper casts light on customer heterogeneity associated with different dimensions of vulnerability by using consumer demographics, and indicates that four dimensions of vulnerability exist as cognitive capability, social relations, behaviors, and the institutional protection in health-related sector. These four aspects of vulnerability play a significant role in identifying different shop selection patterns. Findings suggest that efforts to boost store patronage targeting on various consumer groups should have different strategies to reach consumers’ mindsets.