The Role of Statistical Models in the Prediction of Tropical Cyclone Motion

Tropical cyclones (tropical storms, hurricanes, typhoons, etc.) occur over many of the earth's tropical marine areas. Responsibility for tracking and predicting the future course of these storms is assigned to one or more domestic or foreign meteorological services. These services routinely activate a number of statistical and dynamical prediction models as objective guidance preparatory to issuing official forecasts on these storms. In this article, the role of the statistical models in this process is examined.     

Determinants of voluntary executive stock option disclosure in Brazil

This study investigates whether the governance attributes of Brazilian companies are associated with voluntary executive stock option (ESO) disclosure. Results show that Brazilian companies voluntarily disclose very little about their ESO plans, and that board size, presence of a compensation committee, and auditing by a Big 4 firm are significantly related to the degree of voluntary ESO disclosure. We also show that family-controlled companies in Brazil are associated with low voluntary ESO disclosure. Results are robust to a number of specification tests, dependent and explanatory variable measurements, and sample composition. This study has professional and regulatory implications for Brazil and other emerging capital markets. The results underscore the need for stricter rules for executive compensation reporting in Brazil, and they invite policy makers and regulators in emerging markets to consider the effects of company-level governance factors on disclosure incentives.     

Smoothing a Time Series by Segments of the Data Range

We consider the problem of estimating a trend with different amounts of smoothness for segments of a time series subjected to different variability regimes. We propose using an unobserved components model to consider the existence of at least two data segments. We first fix some desired percentages of smoothness for the trend segments and deduce the corresponding smoothing parameters involved. Once the size of each segment is chosen, the smoothing formulas here derived produce trend estimates for all segments with the desired smoothness as well as their corresponding estimated variances. Empirical examples from demography and economics illustrate our proposal.     

Commercial sex between men: A prospective diary‐based study

This paper describes the results of a self‐reporting dairy completed by 186 male sex workers (MSWs) over a 2‐week period in Brisbane, Sydney, and Melbourne, Australia. The diary was completed following each commercial sex encounter by the MSW. The results reveal that MSWs reported 2088 commercial sex encounters during the study period, with an average of 11.2 encounters per MSW. The majority of sex encounters took place in either the client's or the MSW's residence, with significant variations by city. The average sexual encounter lasted 70 minutes, and comprised two sexual acts, masturbation and oral sex. Condom use was reported in 67.4% of all the encounters. Using the AIDS Council safe‐sex classification system, the majority of the commercial sex encounters fell in the “safer sex” category; however, there were significant differences by source of clients and place of the encounter. Use of drugs and alcohol reveal interesting patterns: Clients were more likely to use alcohol, while MSWs had significant differences of usage of the different drugs. This study demonstrates that the majority of MSWs are offering and practicing safe sex behaviours, however, MSWs working in the street setting are still likely to be practising unsafe sex. Male sex work is becoming an organised business and this provides opportunities to implement further public health interventions.     

A class of semiparametric transormation frailty models with application to estimating treatment effects and heterogenity in aids clinical traials

Muitivariate failure time data are common in medical research; com¬monly used statistical models for such correlated failure-time data include frailty and marginal models. Both types of models most often assume pro¬portional hazards (Cox, 1972); but the Cox model may not fit the data well This article presents a class of linear transformation frailty models that in¬cludes, as a special case, the proportional hazards model with frailty. We then propose approximate procedures to derive the best linear unbiased es¬timates and predictors of the regression parameters and frailties. We apply the proposed methods to analyze results of a clinical trial of different dose levels of didansine (ddl) among HIV-infected patients who were intolerant of zidovudine (ZDV). These methods yield estimates of treatment effects and of frailties corresponding to patient groups defined by clinical history prior to entry into the trial.     

Computational and statistical efficiency of semiparametric gls estimators

In this note, we report a dramatic improvement in the computational efficiency of semiparametric generalized least squares(SGLS) estimation. Computation of SGLS estimates no longer presents serious problems with data sets of moderate size. We also correct a numerical error in the standard errors of the SGLS estimates reported in our recent paper in this journal (Horowitz and Neumann, 1987). The corrected standard errors of SGLS are comparable to those we reported for quantile estimates.     

Uncertainty, Contrariness and the Double-bind: Middle Managers' Reactions to Changing Contracts

This article describes the emerging changes in psychological contracts being experienced by British middle managers in relation to their employing organizations, the middle managers' negative reactions to these changes and organizational responses to such negativity. By analysing case studies of 16 organizations, a classification of changes to five elements of the psychological contract are identified: knowledge, motivation, goals and means, role behaviour and ethics. By analysing the semi-structured interviews of 37 middle managers, selected from a much larger database for their obvious negative reactions, a continuum of such reactions is considered: uncertainty, contrariness and double-bind. This consideration leads, then, to suggestions for further research.     

Development and Consideration of Global Policies for Managing the Future Risks of Poliovirus Outbreaks: Insights and Lessons Learned Through Modeling

The success of the Global Polio Eradication Initiative promises to bring large benefits, including sustained improvements in quality of life (i.e., cases of paralytic disease and deaths avoided) and costs saved from cessation of vaccination. Obtaining and maintaining these benefits requires that policymakers manage the transition from the current massive use of oral poliovirus vaccine (OPV) to a world without OPV and free of the risks of potential future reintroductions of live polioviruses. This article describes the analytical journey that began in 2001 with a retrospective case study on polio risk management and led to development of dynamic integrated risk, economic, and decision analysis tools to inform global policies for managing the risks of polio. This analytical journey has provided several key insights and lessons learned that will be useful to future analysts involved in similar complex decision-making processes.     

The allocation of time to social and leisure activities as social indicators for the integration of aged ethnic minorities

One way in which a better understanding of social indicators to be employed in assessing the degree of social integration of aged ethnic minorities is to determine their time-use patterns for various daily activities. This paper reports on a research project undertaken in a planned community of La Villeneuve, France, which examines (a) the social context in which various activities took place, and (b) the duration and frequency of the activities. This was achieved through the combined techniques of time-budget analysis, social network mapping, and participant observations. Our data provides another dimension appropriate for social indicators research.     

Ask Prices, Offers, and Time to Sale in an Online Exchange

By examining an online computer exchange, we find that sellers who place higher nonbinding ask prices have higher outstanding offers and remain on the exchange longer, suggesting a willingness to hold out for higher offers. Additionally, higher ask prices deter buyers from making offers. The results are stronger in thinner market segments, suggesting that gains from waiting for a high price are greater when buyers' tastes are idiosyncratic. These relationships are consistent with models in which buyers engage in costly search and suggest that online exchanges may not eliminate the frictions related to bilateral transactions.