Zero-inflated count regression models with applications to some examples

In this paper, we employed SAS PROC NLMIXED (Nonlinear mixed model procedure) to analyze three example data having inflated zeros. Examples used are data having covariates and no covariates. The covariates utilized in this article have binary outcomes to simplify our analysis. Of course the analysis can readily be extended to situations with several covariates having multiple levels. Models fitted include the Poisson (P), the negative binomial (NB), the generalized Poisson (GP), and their zero-inflated variants, namely the ZIP, the ZINB and the ZIGP models respectively. Parameter estimates as well as the appropriate goodness-of-fit statistic (the deviance D) in this case are computed and in some cases, the Pearson’s X ² statistic, that is based on the variance of the relevant model distribution is also computed. Also obtained are the expected frequencies for the models and GOF tests are conducted based on the rule established by Lawal (Appl Stat 29:292–298, 1980). Our results extend previous results on the analysis of the chosen data in this example. Further, results obtained are very consistent with previous analyses on the data sets chosen for this article. We also present an hierarchical figure relating all the models employed in this paper. While we do not pretend that the results obtained are entirely new, however, the analyses give opportunities to researchers in the field the much needed means of implementing these models in SAS without having to resort to S-PLUS, R or Stata.     

To Screen or Not to Screen? Using the Internet for Selection Decisions

Organizations are increasingly relying on Internet searches and social networking websites to uncover detailed and private information about job applicants. Such Internet screening techniques have the potential to provide additional information beyond that found using traditional screening approaches. However, questions regarding the legality and appropriateness of this practice, as well as issues regarding the standardization, reliability, and validity of the information obtained, need to be addressed. The current work describes these issues associated with Internet screening and provides recommendations to help ensure this practice is used appropriately in organizations. Suggestions for future research on Internet screening are also discussed.     

How do quotes and prices evolve around isolated informed trades?

This article investigates the order imbalance and price behavior of trades and quotes around isolated informed trades intraday. Different patterns of order flows around informed trades are documented because of the originating stock exchange, the type of informed trader, the size of the order, and the type of the firm whose shares are traded. The informed trader acts contrarian to prior trades. Informed purchases follow price declines, and sales are after price increases. The informed trade is recognized by the market maker. The purchase is executed at a significantly higher price, while the sale is executed at a significantly lower price. Trades contain more information if the insiders are at small firms. Larger orders and orders by top executives also contain more information. The order imbalance changes around an informed trade. Orders are seller-initiated prior to the purchase and become buyer-initiated after the trade. On the other hand, the order imbalance changes from buyer- to seller-initiated right around insider sales. Reversals in order imbalance are more pronounced for informed trades in small firms, for larger trades, and by top executives. There are important policy implications of the results. The recognition of informed trades by market makers justifies more scrutiny by the Securities and Exchange Commission in order to ensure fair trading.     

DISCOUNT RATES AND ENERGY EFFICIENCY

Empirical studies provide compelling evidence that economic agents do not adopt the complete range of energy-efficient technologies that are cost-effective under prevailing prices and market conditions. Analysts commonly attribute this anomaly to the use of high discount rates in energy-related decisions-an interpretation that is difficult to reconcile with standard models of rational choice. This paper recasts the controversy from the perspective of economic theory and finds that market failures related to asymmetric information, bounded rationality, and transaction costs are major contributors to the so-called "efficiency gap."     

RISK OF ACCIDENTS AND THE POLICY OF FORCED RETIREMENT

In 1960, the Federal Aviation Administration put in place the Age 60 rule forcing airline pilots to retire upon reaching the age of 60 years. This paper uses data from the National Transportation Safety Board and the Federal Aviation Administration to determine if having pilots above 59 years of age carries a social cost. Statistical evidence indicates that the severity of aircraft accidents is related to pilot age for some classes of pilots but not for others. Findings are that small-airplane accidents tend to be more severe for pilots over 59 with private and commercial licenses than for younger pilots with equal qualifications. Thus, some (though not convincing) evidence suggests that private and commercial pilots above 59 years of age impose a greater social cost on the flying public than do younger pilots. However, among ATP pilots—that is, those who are licensed to fly large airplanes—no evidence indicates that pilots over 59 have more severe accidents when flying small airplanes than do younger ATP pilots flying such airplanes. Moreover, no evidence indicates that age is a factor in serious and fatal accidents for ATP pilots flying large airplanes up to the mandatory retirement age of 60 years. The extra screening and training of ATP pilots may explain the differences in accident severity between these and other pilots.     

FDI in space: Spatial autoregressive relationships in foreign direct investment

There are a number of theoretical reasons why foreign direct investment (FDI) into a host country may depend on the FDI in proximate countries. Such spatial interdependence has been largely ignored by the empirical FDI literature, with only a couple recent papers accounting for such issues in their estimation. This paper conducts a general examination of spatial interactions in empirical FDI models using data on US outbound FDI activity. We find that estimated relationships of traditional determinants of FDI are surprisingly robust to inclusion of terms to capture spatial interdependence, even though such interdependence is estimated to be significant. However, we find that both the traditional determinants of FDI and the estimated spatial interdependence are quite sensitive to the sample of countries one examines.