人口规模、经济增长与碳排放:经验证据及国际比较

根据国际能源署（IEA）公布的1971—2008年碳排放数据,探讨中国与典型发达国家、发展中国家（G8＋5）人口规模、经济增长与碳排放变化的差异性。结果表明：随着GDP增长,中国碳排放快速增长,人均碳排放已超过世界平均水平;单位GDP碳排放持续降低,但依然高于世界平均水平。利用秩相关系数检验人均GDP与单位GDP碳排放,发现7个发达国家均呈显著下降趋势,发展中国家南非、中国呈显著下降趋势,巴西、印度、墨西哥呈上升趋势但并不显著;人均GDP与人均碳排放秩相关系数表明,7个发达国家中,美国、法国、德国、英国呈显著下降趋势,加拿大呈不显著上升趋势,日本、意大利呈显著上升趋势;5个发展中国家处于工业化快速发展阶段,能源消费急剧增加,随着人均GDP增长,人均碳排放均呈显著上升趋势。基于此,归纳出世界主要发达国家和发展中国家人口增长、经济增长与碳排放变动的三种模式。     

Firm Size Distribution and Growth*

Abstract Empirical documentation of the sectoral distribution of firm size for a set of European countries reveals substantial differences. We study the relationship between productivity growth at the industry level and size structure. A positive and robust relation is found between average firm size and growth. We ask why size should matter for growth by considering the role of innovation to construct a test based on the differential effect of size on growth according to various indicators of R&D intensity. Our results indicate that larger size fosters productivity growth because it allows firms to take advantage of all the increasing returns associated with R&D. We argue that our test can be interpreted as a test of reverse causality, which lends support to the view that firm size has a causal impact on growth.     

Robustness issues in multilevel regression analysis

A multilevel problem concerns a population with a hierarchical structure. A sample from such a population can be described as a multistage sample. First, a sample of higher level units is drawn (e.g. schools or organizations), and next a sample of the sub‐units from the available units (e.g. pupils in schools or employees in organizations). In such samples, the individual observations are in general not completely independent. Multilevel analysis software accounts for this dependence and in recent years these programs have been widely accepted. Two problems that occur in the practice of multilevel modeling will be discussed. The first problem is the choice of the sample sizes at the different levels. What are sufficient sample sizes for accurate estimation? The second problem is the normality assumption of the level‐2 error distribution. When one wants to conduct tests of significance, the errors need to be normally distributed. What happens when this is not the case? In this paper, simulation studies are used to answer both questions. With respect to the first question, the results show that a small sample size at level two (meaning a sample of 50 or less) leads to biased estimates of the second‐level standard errors. The answer to the second question is that only the standard errors for the random effects at the second level are highly inaccurate if the distributional assumptions concerning the level‐2 errors are not fulfilled. Robust standard errors turn out to be more reliable than the asymptotic standard errors based on maximum likelihood.     

GOVERNMENT SIZE AND GROWTH: A SURVEY AND INTERPRETATION OF THE EVIDENCE

Abstract The literature on the relationship between the size of government and economic growth is full of seemingly contradictory findings. This conflict is largely explained by variations in definitions and the countries studied. An alternative approach – of limiting the focus to studies of the relationship in rich countries, measuring government size as total taxes or total expenditure relative to GDP and relying on panel data estimations with variation over time – reveals a more consistent picture. The most recent studies find a significant negative correlation: an increase in government size by 10 percentage points is associated with a 0.5% to 1% lower annual growth rate. We discuss efforts to make sense of this correlation, and note several pitfalls involved in giving it a causal interpretation. Against this background, we discuss two explanations of why several countries with high taxes seem able to enjoy above average growth. One hypothesis is that countries with higher social trust levels are able to develop larger government sectors without harming the economy. Another explanation is that countries with large governments compensate for high taxes and spending by implementing market‐friendly policies in other areas. Both explanations are supported by ongoing research.     

Properties of Census Dual System Population Size Estimators

We study parametric and non‐parametric approaches for assessing the accuracy and coverage of a population census based on dual system surveys. The two parametric approaches being considered are post‐stratification and logistic regression, which have been or will be implemented for the US Census dual system surveys. We show that the parametric model‐based approaches are generally biased unless the model is correctly specified. We then study a local post‐stratification approach based on a non‐parametric kernel estimate of the Census enumeration functions. We illustrate that the non‐parametric approach avoids the risk of model mis‐specification and is consistent under relatively weak conditions. The performances of these estimators are evaluated numerically via simulation studies and an empirical analysis based on the 2000 US Census post‐enumeration survey data.     

基于集对分析法的地区大中型工业企业自主创新能力评价

为了对地区大中型工业企业自主创新能力进行全面、科学的评价,基于集对分析法,提出了地区大中型工业企业自主创新能力评价指标体系及综合评价模型。通过对我国30个省市区大中型工业企业的实证分析,表明该方法科学简便,具有很好的实用价值。     

Leadership and group size: An experiment

Our experimental results suggest that the effectiveness of leading by example decreases with group size. The discrepancy between the leaders' and followers' incentives increases with group size. Thus, as group size increases, followers more often refuse to follow their leaders.     

关于卷制螺旋滚子结构尺寸的理论分析

卷制螺旋滚子是一种全新理念的滚子,可以有效地识别出螺旋滚子结构尺寸与变形能之间的相互关系,该滚子的周身遍布缝隙,其区别于普通滚子的一个最大特点就是可以吸收冲击能,既解决普通滚子在高速多冲作用下的早期断裂问题,又提高滚子的抗冲击性能。为此,文章主要针对有关于卷制螺旋滚子结构尺寸的理论,进行简单的分析和探讨。     

分拣导入物料的投影尺寸及近似体积测量计算方法

分析了目前自动化物流分拣输送系统在物料导入输送环节的工艺特点和设备控制现状,并结合应用光电检测、工业可编程控制等技术,针对水平交叉带分拣输送机应用场景,对其中物料导入控制环节所面临的物料外形尺寸测量和计算问题,提出了基于物料轮廓最大值检测、尺寸特征捕捉、长宽比关系判断等要素来对物料投影尺寸进行测量的计算方法,具有数据采集实时、程序编写简单、运算量少等特点;同时基于对导入输送的物料进行横向、纵向的截面段断层扫描测量并累加计算,以较低的器件成本及较少的控制器程序运算量,实现对物料体积的近似测量计算,是一种较为经济和可取的控制计算方法。     

TO ADMIT OR NOT TO ADMIT: THE QUESTION OF RESEARCH PARK SIZE

A theoretical model is used to explore the determinants of the optimum size of a private research park and the effect of university affiliation on that optimum size. Parks are assumed to operate as cooperatives where costs are equally shared among the member firms, and optimality occurs when the firms’ average net benefits are maximized. To achieve this, existing members of a park will limit the park's size, denying entry to firms who wish to join and are willing to share the costs. University affiliation may either increase or decrease the optimum size of a park.