不动产项目与证券的混合投资组合模型

分散投资可以降低投资整体的风险并在长期投资中获得更多收益,本文提出了一个不动产项目与证券的混合投资组合模型,用半绝对偏差风险函数来计算资产组合在各个离散时间点的风险,并将双目标模型转化为单目标模型然后加以解决。同时,我们在最后将举一个例子来说明本模型。     

Manager bonding and the technical efficiency of cooperative credit unions-parametric and non-parametric analyses

We engage parametric and non-parametric approaches to analyze unbalanced data (2012–16) from 225 credit unions in Ghana. The non-parametric analysis involves using data envelopment analysis to assess the technical efficiency of the credit unions. We show that most of them are not technically efficient. The average five-year overall technical efficiency and pure technical efficiency scores of a credit union are 0.87 and 0.91 respectively. Targeted at inquiring whether manager bonding significantly connects with the technical efficiency of credit unions, the parametric analysis which involves the use of probit and logit regression techniques, shows that, generally, the bonding of managers hurts the technical efficiency of credit unions. We are, thus, led to the conclusion that bonding of managers may not be in the best interest of credit unions in Ghana.     

R&D subsidies and private R&D expenditures: evidence from Italian manufacturing data

This paper uses a comprehensive firm level data set for the manufacturing sector in Italy to investigate the effect of government support on privately financed R&D expenditure. Estimates from a non‐parametric matching procedure suggest that public assistance has a positive effect on private R&D investment in the sense that the recipient firms achieve more private R&D than they would have without public support. This indicates that the possibility of perfect crowding out between private and public funds can be rejected. Furthermore, in this sample of Italian firms, tax incentives appear to be more effective than direct grants. The paper also examines whether public funding affects the financial sources available for R&D and finds that grants encourage the use of internal sources. The results also show some evidence of positive effects on credit financing for R&D.     

THE PREDICTABILITY OF STOCK MARKET RETURNS IN SOUTH AFRICA: PARAMETRIC VS. NON‐PARAMETRIC METHODS

This paper compares the forecasting performance of a sub‐class of univariate parametric and non‐parametric models in predicting stock market returns in South Africa. To account for conditional heteroskedasticity in stock returns data, the non‐parametric model is generated by the conditional heteroskedastic non‐linear autoregressive (NAR) model, while the parametric model is produced by the generalised autoregressive conditional heteroskedastic in mean (GARCH‐M) model. The results of the paper show that the NAR as a non‐parametric model performs better than the GARCH‐M model in short‐term forecasting horizon, and this indicates the importance of a distribution‐free model in predicting stock returns in South Africa.     

货车转向架参数化设计系统的开发

文章将参数化设计技术应用于货车转向架的设计,以Pro/Engineer为设计开发平台,以VisualC++6.0为集成开发环境,研究开发了基于参数化设计技术的货车转向架设计系统。     

Intergenerational Earnings Mobility in Norway: Levels and Trends*

Using longitudinal data for Norwegian children born in 1950, 1955, 1960 and 1965, we find a relatively high degree of earnings mobility. There is no tendency toward decreasing mobility over the cohorts. Conditioning on the position in the earnings distribution, the analysis indicates quite high mobility in the middle of the distribution and somewhat more persistence at the top and bottom. This approach also reveals increased mobility over time for sons, but a less clear picture for daughters.     

Semiparametric estimation and testing in a model of environmental regulation with adverse selection

We consider a principal–agent model of environmental regulation with adverse selection, where firms are regulated through contracts. We show how the model allows to recover information on structural cost parameters. We use a semiparametric method to estimate consistently such parameters without specifying the distribution of the agents private information. We also show how to check for the specification of the econometric model, as well as auxiliary parametric assumptions, by means of specification tests based on nonparametric estimation. Results are used to discuss a selection of economic issues related to environmental regulation.First version received: August 2002/Final version received: November 2003Previous versions of this work were presented at Seminaire INRA-IDEI, Toulouse, the conference on Applications of semiparametric methods for micro-data, Tilburg, and seminars at UC Berkeley, University of Wisconsin–Madison, CREST, and INRA-LEA. We are indebted to participants, and especially Michael Visser, for their comments. We thank two referees for helpful comments. Financial support from the Conseil Régional Midi-Pyrénées and from INRA is gratefully acknowledged.     

An Empirical Test of Environmental Kuznets Curve for Water Pollution

The Environmental Kuznets Curve (EKC) on water pollution was investigated with both semiparametric and parametric models using watershed level data for the state of Louisiana, USA. The parametric model indicated the turning points within the range $10241–$12993, $6636–$13877, and $6467–$12758 for nitrogen (N), phosphorus (P), and dissolved oxygen (DO), respectively. However, only the parameters associated with N EKC were found to be significant. Model specification tests rejected parametric models in favor of semiparametric specification for P but not for N and DO.     

Misspecification Preferred: The Sensitivity of Inefficiency Rankings

Ruggiero (European Journal of Operational Research 115, 555–563. 1999) compared the two popular parametric frontier methods for cross-sectional data—the stochastic frontier and the corrected OLS—in a simulation study. He demonstrated that the inefficiency ranking accuracy of the established stochastic frontier is uniformly inferior to that of the misspecified Corrected OLS (COLS) (which lacks an error term). The reason for his result remains unclear, however. In this paper, a more extensive simulation study is therefore conducted to find out whether the superiority of COLS is simply due to small sample sizes or to poor performance of the inefficiency level estimator.JEL Classification: C1,C2,C5     

Estimation of innovation diffusion models with application to a consumer durable

A class of birth processes having a variety of practical applications in penetration of new services and products is considered. Typically, statistical inferences on these models are performed by means of simple error structures placed on the deterministic analogs of the underlying stochastic processes. Motivated by the poor performance of conventional estimation methods, the problem of estimating the parameters of these models is readdressed. We develop necessary formulae for performing the maximum likelihood estimation and weighted least squares estimation methods, and demonstrate their superiority through analyses of some real data and simulation studies.