A general class of estimators for estimating population mean using auxiliary information

Summary A general class of estimators for estimating the population mean of the character under study which make use of auxiliary information is proposed. Under simple random sampling without replacement (SRSWOR), the expressions of Bias and Mean Square Error (MSE), up to the first and the second degrees of approximation are derived. General conditions, up to the first order approximation, are also obtained under which any member of this class performs more efficiently than the mean per unit estimator, the ratio estimator and the product estimator. The class of estimators in its optimum case, under the first degree approximation, is discussed. It is shown that it is not possible to obtain optimum values of parameters “a”, “b” and “p”, that are independent of each other. However, the optimum relation among them is given by (b−a)p=ρ C _y/C _x. Under this condition, the expression of MSE of the class is that of the linear regression estimator.     

The effect of time-varying covariances on asset risk premia

In this article we examine an intertemporal capital asset pricing model (CAPM) that allows for time-varying conditional covariances that are assumed to follow a multivariate integrated generalized autoregressive conditional heteroscedastic (IGARCH) process. The resulting pricing equation includes idiosyncratic risk premia in addition to the usual market beta. Empirical analysis based on ten size and ten industry portfolios reveals significant idiosyncratic premia for most portfolios. Overall, we reject the static CAPM in favor of the intertemporal CAPM.     

Equilibrium urban unemployment in developing countries: is migration the culprit?

"This paper challenges the prediction of Todaro's model of rural-to-urban migration that an 'increase in urban employment increases urban unemployed.' It is shown that if the urban demand for labor is isoelastic or inelastic, creation of urban jobs causes urban unemployment to decline and urban-to-rural migration to take place. Moveover, urban job creation always reduces the rate of urban unemployment. The paper then remodels the urban job search process and derives the result that equilibrium urban unemployment would not vanish even if the urban-rural wage gap were eliminated." The geographical focus is on developing countries.     

Static Hedging of Exotic Options

This paper develops static hedges for several exotic options using standard options. The method relies on a relationship between European puts and calls with different strike prices. The analysis allows for constant volatility or for volatility smiles or frowns.     

Could we have predicted the recent downturn in the South African housing market?

This paper develops large-scale Bayesian Vector Autoregressive (BVAR) models, based on 268 quarterly series, for forecasting annualized real house price growth rates for large-, medium- and small-middle-segment housing for the South African economy. Given the in-sample period of 1980:01–2000:04, the large-scale BVARs, estimated under alternative hyperparameter values specifying the priors, are used to forecast real house price growth rates over a 24-quarter out-of-sample horizon of 2001:01–2006:04. The forecast performance of the large-scale BVARs are then compared with classical and Bayesian versions of univariate and multivariate Vector Autoregressive (VAR) models, merely comprising of the real growth rates of the large-, medium- and small-middle-segment houses, and a large-scale Dynamic Factor Model (DFM), which comprises of the same 268 variables included in the large-scale BVARs. Based on the one- to four-quarters-ahead Root Mean Square Errors (RMSEs) over the out-of-sample horizon, we find the large-scale BVARs to not only outperform all the other alternative models, but to also predict the recent downturn in the real house price growth rates for the three categories of the middle-segment-housing over the period of 2003:01–2008:02.     

帮助贫困人口

在贫困国家，用于教育与卫生保健的支出能促进人力资本的发展，并帮助它们实现千年发展目标，不过政府必须敢于承担责任。     

Foreign capital and technology transfer in a dynamic model

We consider a dynamic three-sector dual-economy model when the technology transfer takes place from the foreign enclave to the labor-intensive domestic enclave. The long-run equilibrium and the comparative steady-state effects are analyzed. It is shown that the policy of subsidization to the foreign enclave may satisfy the conflicting tasks of raising national income and lowering unemployment simulataneously in the long run. Subsidization to a domestic enclave does not satisfy both the objectives.     

Estimation of the precision matrix of multivariate Pearson type II model

In this paper, the problem of estimating the precision matrix of a multivariate Pearson type II-model is considered. A new class of estimators is proposed. Moreover, the risk functions of the usual and the proposed estimators are explicitly derived. It is shown that the proposed estimator dominates the MLE and the unbiased estimator, under the quadratic loss function. A simulation study is carried out and confirms these results. Improved estimator of tr (Σ ⁻¹) is also obtained.     

Gender Characterizations in Entrepreneurship: A Multi‐Level Investigation of Sex‐Role Stereotypes about High‐Growth,Commercial, and Social Entrepreneurs

The purpose of this study is to cast new light on possible gender biases in implicit theories people hold about various forms of entrepreneurial activity. Using social role theory, we delve into sex‐role stereotypes associated with high‐ and low‐growth entrepreneurship and commercial and social entrepreneurship. Predictions were tested with an experimental design using both a between‐subject design to capture group‐level stereotypes and a within‐subject design to capture individual‐level stereotypes. Findings reveal that commercial and high‐growth entrepreneurs are perceived as more similar to men than to women and higher on agency than communality. Conversely, low‐growth entrepreneurs are perceived as more similar to women than men, and higher on communality than agency. Social entrepreneurs are uniquely perceived as similar to both men and women, though they are also considered higher on agency than communality. Interestingly, female, but not male respondents, perceive some overlap between the feminine gender role and high‐growth and commercial entrepreneurship. Notably, those higher on modern sexism perceive less overlap between entrepreneurship and femininity. Taken together, our results suggest that commercial high‐growth entrepreneurship is most strongly male‐typed, which is likely to be problematic for women (and non‐traditional men) wanting to start growth‐oriented ventures. Implications and directions for future research are discussed.     

How Task-Facilitative Interactive Tools Foster Buyers’ Trust in Online Retailers: A Process View of Trust Development in the Electronic Marketplace

While there is a sustained interest in research focusing on issues relating to trust development in the electronic marketplace, significant gaps remain in the literature. In particular, little is known of the underlying processes that may be occurring in online trust development. For example, research suggests that factors such as site design and navigability are among the factors that impact trust perceptions. Extant literature, however, is largely silent about why certain trust-related effects are observed in online environments. In this paper, we propose a new process-centric perspective for understanding the formation of online trust—through buyer's assessment of the e-retailer's assistive intent, implicitly embedded in task-facilitative interactive tools. Specifically, we develop and test a model delineating the relationship between seller's provision of interactive product information management and product information comprehension tools, buyer's perceptions of seller's assistive intent, and buyer's initial trust in the seller. The results of two studies provide support for the trust-enhancing effects of task-facilitative informational tools and the mediating role of buyer's perceptions of seller's assistive intent. Importantly, these effects occur without any explicit expressions of seller's intentions. The results also suggest that the efficacy of interactive informational tools in engendering perceptions of seller's assistive intent, and hence trust, varies with the buyer's level of involvement with and knowledge of the product category.