An alternate version of the conceptual predictive statistic based on a symmetrized discrepancy measure

The conceptual predictive statistic, C_p, is a widely used criterion for model selection in linear regression. C_p serves as an estimator of a discrepancy, a measure that reflects the disparity between the generating model and a fitted candidate model. This discrepancy, based on scaled squared error loss, is asymmetric: an alternate measure is obtained by reversing the roles of the two models in the definition of the measure. We propose a variant of the C_p statistic based on estimating a symmetrized version of the discrepancy targeted by C_p. We claim that the resulting criterion provides better protection against overfitting than C_p, since the symmetric discrepancy is more sensitive towards detecting overspecification than its asymmetric counterpart. We illustrate our claim by presenting simulation results. Finally, we demonstrate the practical utility of the new criterion by discussing a modeling application based on data collected in a cardiac rehabilitation program at University of Iowa Hospitals and Clinics.     

The role of tobacco taxes in starting and quitting smoking: Duration analysis of British data

The annual 5% increase in tobacco taxes in real terms proposed in the recent White Paper on smoking has reaffirmed the commitment of successive UK Governments to above-inflation increases in tobacco taxation to encourage people to stop smoking. This paper presents evidence on the determinants of starting and quitting smoking by using data from the British Health and Lifestyle Survey and is the first to identify tax elasticities for starting and quitting smoking using British data. Self-reported individual smoking histories are coupled with a long time series for the tax rate on cigarettes to construct a longitudinal data set. Estimates are obtained for the effect of above-inflation tax rises on the age of starting smoking and the number of years of smoking. The estimates of the tax elasticity of the age of starting smoking are 0.16 for men and 0.08 for women. The estimates of the tax elasticity of quitting are −0.60 for men and −0.46 for women. These are robust to different specifications.     

SYMBOLIC POLITICS IN THE INFORMATION AGE: THE 1996 REPUBLICAN PRESIDENTIAL CAMPAIGNS IN CYBERSPACE

This paper traces the use of the World Wide Web as a medium of political communication during the 1996 American presidential campaigns. Beginning with the Republican campaigns' use of the medium during the primary election season, a typology of uses of the web is outlined. While all campaigns felt it necessary to participate in the World Wide Web, different candidates used the medium differently. Furthermore, no campaign made full use of the much-publicized interactive capacity of the web; they used it more as a new means of transmitting traditional mass-media literature (video, graphics, etc.) and as a way of providing access to large volumes of campaign information (voting records, speeches, position papers, etc.).     

Internalising and externalising children's behaviour problems in Britain and the US: relationships to family resources1

A large sample of British children (n=994) of varying ages (7–18 years) and a large sample of American children (n=886) of varying ages (7–16 years) were rated by their mothers using respectively the Rutter Child Scale A and the Behaviour Problems Index both of which cover a variety of behavioural problems. Factor analysis of the behavioural scales distinguished externalising and internalising dimensions of behaviour in both countries. We examined whether children's experiences of family change, cognitive ability and family adversity including economic deprivation were associated with differences in the prevalence of the behavioural dimensions. Mean cognitive scores decreased significantly with increasing level of externalising behavioural problems in British and American children but showed no significant relationship to levels of internalising behaviour problems in either sample. Among American children internalising and externalising behavioural problems were related to experience of non‐intact family structures and measures of family adversity. Externalising behavioural problems were related to measures of family adversity among British boys and girls but were only related to experience of non‐intact family structures in the sample of British girls. Among British girls, internalising behavioural problems were also related to non‐intact family structures. The associations between non‐intact family structures and behavioural problems were independent of measures of economic deprivation in both samples of children. This study documents some of the background factors which affect children's behavioural and cognitive outcomes. Unlike children's family structure economic deprivation can be influenced through policy intervention, and the analysis supports the view that relieving economic deprivation would help improve children's behavioural outcomes. Copyright © 2000 John Wiley & Sons, Ltd.     

Nonparametric Identification under Discrete Variation

This paper provides weak conditions under which there is nonparametric interval identification of local features of a structural function that depends on a discrete endogenous variable and is nonseparable in latent variates. The function delivers values of a discrete or continuous outcome and instruments may be discrete valued. Application of the analog principle leads to quantile regression based interval estimators of values and partial differences of structural functions. The results are used to investigate the nonparametric identifying power of the quarter‐of‐birth instruments used in Angrist and Krueger's 1991 study of the returns to schooling.     

POLITICAL REPUTATIONS AND CAMPAIGN PROMISES

We analyze conditions under which candidates' reputations may affect voters' beliefs over what policy will be implemented by the winning candidate of an election. We develop a model of repeated elections with complete information in which candidates are purely ideological. We analyze an equilibrium in which voters' strategies involve a credible threat to punish candidates who renege on their campaign promises and in which all campaign promises are believed by voters and honored by candidates. We characterize the maximal credible campaign promises and find that the degree to which promises are credible in equilibrium is an increasing function of the value of a candidate's reputation. (JEL: D8)     

On E‐Auctions for Procurement Operations

Electronic auctions have revolutionized procurement in the last decade. In many situations, they have replaced negotiations for supplier selection and price setting. While they have often greatly reduced transaction costs and increased competition, they have also encountered problems and resistance from suppliers resenting their intrusion on cooperative supplier/buyer relationships. In response to these issues, procurement auctions have evolved in radical new directions. Buyers use business rules to limit adverse changes. Some procurement auctions allow bidders to offer variants in the specifications of products to be supplied. Most important, some suppliers are allowing bidders to bid on packages of items, not just individual items. This tends to change procurement auctions from zero‐sum fights over supplier profit margins to win‐win searches for synergies. These changes have opened up many new research areas. Researchers are trying to improve how to deal with the computational issues involved in package auctions and to analyze the new auctions forms that are evolving. In general, equilibrium incentives are not known, and dealing with ties in package auctions is an issue. Computer scientists are analyzing the use of computerized bidding agents. Mechanisms that combine auctions with fixed buy prices or with negotiations need to be analyzed.     

The electronic face of government in the internet age: borrowing from Murray Edelman

The issue of legitimation by political elites has been a central concern of political scientists for many years. This article draws upon the work of Murray Edelman who was instrumental in analysing this relationship between rulers and ruled, the relatively powerful and relatively powerless, through an understanding of language, symbolism and the manipulation of information. It concludes with the contention that the Internet offers the prospect for governments to create new 'electronic faces', which act to support a symbolic architecture of power.     

Improving coverage accuracy of nonparametric prediction intervals

Methods are suggested for improving the coverage accuracy of intervals for predicting future values of a random variable drawn from a sampled distribution. It is shown that properties of solutions to such problems may be quite unexpected. For example, the bootstrap and the jackknife perform very poorly when used to calibrate coverage, although the jackknife estimator of the true coverage is virtually unbiased. A version of the smoothed bootstrap can be employed for successful calibration, however. Interpolation among adjacent order statistics can also be an effective way of calibrating, although even there the results are unexpected. In particular, whereas the coverage error can be reduced from O ( n ^-1) to orders O ( n ^-2) and O ( n ^-3) (where n denotes the sample size) by interpolating among two and three order statistics respectively, the next two orders of reduction require interpolation among five and eight order statistics respectively.