On Some Characteristics of Gaussian Covariance Functions

The concepts of isotropy/anisotropy and separability/non‐separability of a covariance function are strictly related. If a covariance function is separable, it cannot be isotropic or geometrically anisotropic, except for the Gaussian covariance function, which is the only model both separable and isotropic. In this paper, some interesting results concerning the Gaussian covariance model and its properties related to isotropy and separability are given, and moreover, some examples are provided. Finally, a discussion on asymmetric models, with Gaussian marginals, is furnished and the strictly positive definiteness condition is discussed.     

高校知识溢出与企业创新绩效

本文利用全样本数据探讨了作为创新和知识溢出微观主体的高校对企业创新绩效的影响。本文通过ArcGIS测算了2007—2015年上市公司所在地周边全部高校数量,并以企业研发投入金额、发明专利衡量企业创新水平,利用Anselin et al.(2000)的KPF方程,采用双聚类OLS检验高校知识溢出对企业创新行为的影响效应与机制。研究发现:第一,高校知识溢出对企业研发创新投入和有效创新产出均具有显著促进作用;第二,知识溢出效应具有显著的地理邻近性特征,而行政边界关联影响较弱;第三,高校知识溢出通过提高企业研发投入,提升员工和管理层人力资本,进而影响企业创新绩效。进一步研究表明,空间异质性、高校异质性、企业异质性、中心城市集聚效应、高铁开通等因素导致高校知识溢出效应存在差异。     

Investigating the solvency of brazilian credit unions using a proportional hazard model

Abstract ** : Due to high interest rates and bank spreads, the number of credit unions in Brazil has increased over recent years. As financial institutions, these cooperatives need tools to signal impending financial problems. This paper focuses on one tool that can be used to evaluate credit union solvency: the Cox Proportional Hazards Model. A sample of 80 credit unions from the Brazilian state of Minas Gerais was selected to supply data. The analysis period is between December 2001 and June 2003. The results indicate that the relevant indicators for insolvency prediction are, in descending order of predictive ability, General Liquidity, Salary and Benefit Expenses, and the Loan/Equity Ratio. In general, results produced using the delineated theoretical model were in consonance with international literature .     

Enticing the Stork: Can we Evaluate Pro‐Natal Policies Before Having Children?

Aside from immigration, the only meaningful demographic lever available to policymakers attempting to moderate the rate of ageing is the birth rate. This article departs from previous analyses of pro‐natal policies by studying determinants of pro‐natal options ex ante, which represents an advantage for policymakers looking to craft policies with prior knowledge of whether or not a demographic policy will have a significant effect. Our multinomial regression model for a US sample involving college students shows that the preferred choice of pro‐natal incentive is dependent on gender, economic class, number of planned children and migrant status. We find that females are more likely than males to choose any pro‐natal incentive over no incentive. The highest odds for increasing planned number of children are for maternity leave and parental leave options. Respondents associating themselves with the poorest economic class are more likely to choose daycare or government grant as pro‐natal options.     

Search Engine Optimization: What Drives Organic Traffic to Retail Sites?

The lion's share of retail traffic through search engines originates from organic (natural) rather than sponsored (paid) links. We use a dataset constructed from over 12,000 search terms and 2 million users to identify drivers of the organic clicks that the top 759 retailers received from search engines in August 2012. Our results are potentially important for search engine optimization (SEO). We find that a retailer's investments in factors such as the quality and brand awareness of its site increases organic clicks through both a direct and an indirect effect. The direct effect stems purely from consumer behavior: The higher the quality of an online retailer, the greater the number of consumers who click its link rather than a competitor in the list of organic results. The indirect effect stems from our finding that search engines tend to place higher quality sites in better positions, which results in additional clicks because consumers tend to click links in more favorable positions. We also find that consumers who are older, wealthier, conduct searches from work, use fewer words, or include a brand name product in their search are more likely to click a retailer's organic link following a product search. Finally, the quality of a retailer's site appears to be especially important in attracting organic traffic from individuals with higher incomes. The beneficial direct and indirect effects of an online retailer's brand equity on organic clicks, coupled with the spillover effects on traffic through other online and traditional channels, leads us to conclude that investments in the quality and brand awareness of a site should be included as part of an SEO strategy.     

When Passion Fades: Disentangling the Temporal Dynamics of Entrepreneurial Passion for Founding

This study examines how and why entrepreneurial passion for founding changes over time. In particular, we propose that in the founding phase of a venture's lifecycle entrepreneurs’ founding identity centrality will remain stable over time. We also propose, however, that in our sample and time period studied, entrepreneurs’ intense positive feelings for founding will decrease over time. On the basis of theories of positive illusion, self‐regulation and role theory, we further hypothesize that venture idea change, change in role ambiguity and entrepreneurs’ feedback‐seeking behaviour are factors that help explain the rate of change in entrepreneurs’ intense positive feelings for founding. Using a three‐wave longitudinal research design, we find that among a sample of 112 entrepreneurs’ identity centrality does not change over time, whereas intense positive feelings for founding decrease over time. Moreover, the more entrepreneurs change their venture ideas, the weaker their decrease in intense positive feelings. Further, we show that entrepreneurs who frequently seek feedback suffer less from reduced positive feelings in response to higher increases in role ambiguity as compared to entrepreneurs who seek less feedback.     

以信息化提升嘉兴秀洲区传统产业研究

本文主要就以信息化提升秀洲区传统产业的问题进行了研讨，分析了秀洲区企业信息化的现状。提出相应的对策和措施。     

A Jump-diffusion Model for Exchange Rates in a Target Zone

We propose a simple jump-diffusion model for an exchange rate target zone. The model captures most stylized facts from the existing target zone models while remaining analytically tractable. The model is based on a modified two-limit version of the C OX , I NGERSOLL and R OSS (1985) model. In the model the exchange rate is kept within the band because the variance decreases as the exchange rate approaches the upper or lower limits of the band. We also consider an extension of the model with parity adjustments, which are modeled as Poisson jumps. Estimation of the model is by GMM based on conditional moments. We derive prices of currency options in our model, assuming that realignment jump risk is idiosyncratic. Throughout, we apply the theory to EMS exchange rate data. We show that, after the EMS crisis of 1993, currencies remain in an implicit target zone which is narrower than the officially announced target zones.     

A Structural Decomposition Analysis of Pollution in the Netherlands

This paper reviews the results of a structural decomposition analysis in which the annual changes in a number of air pollutants and solid waste are decomposed according to their causes. The analysis in this paper is applied with the help of the so-called National Accounting Matrix including Environmental Accounts (NAMEA) for the Netherlands, covering annual data for the period 1987-1998. In a sensitivity analysis it is shown that the average of any pair of so-called 'mirror image' decomposition forms will substantially reduce the variation in the estimates. These mirror image couples are approximately just as reliable as the full average of all decomposition forms. Besides reliable results, the full average also foresees the mutual comparability between the distinguished change factors and is therefore applied in the empirical analyses presented in this paper. The results of these analyses contain the macro-economic developments, results on the industry level as well as a comprehensive overview of the origin and destination of pollution in the Dutch economy that includes the environmental consequences of consumption and international trade.