Trends in marijuana and other illicit drug use among college students: results from 4 Harvard School of Public Health College Alcohol Study surveys: 1993-2001

The authors examined changes in college students' illicit drug use, patterns of polydrug use, and the relationship between students' ages of initiation of substance use and later use of marijuana and other illicit drugs between 1993 and 2001. Data from 119 US colleges and universities in the Harvard School of Public Health College Alcohol Study were used in the study. They found significant increases in percentages of students' use of marijuana in the past 30 days (from 13% to 17%), past year (from 23% to 30%), and lifetime (from 41% to 47%) between 1993 and 2001, with most of the increase occurring between 1993 and 1997. Past 30-day use of other illicit drugs increased from 4% to 7% and past year use increased from 11% to 14%. More than 98% of marijuana and other illicit drug users used another substance. They also either smoked, were binge drinkers, and/or were users of another illicit drug. Drug prevention programs should emphasize heavy alcohol use and smoking and should start when students are in high school or earlier.     

Missing at random (MAR) in nonparametric regression - A simulation experiment

The additive model is considered when some observations on x are missing at random but corresponding observations on y are available. Especially for this model, missing at random is an interesting case because the complete case analysis is expected to be no more suitable. A simulation experiment is reported and the different methods are compared based on their superiority with respect to the sample mean squared error. Some focus is also given on the sample variance and the estimated bias. In detail, the complete case analysis, a kind of stochastic mean imputation, a single imputation and the nearest neighbor imputation are discussed.     

An efficient polynomial space and polynomial delay algorithm for enumeration of maximal motifs in a sequence

In this paper, we consider the problem of enumerating all maximal motifs in an input string for the class of repeated motifs with wild cards. A maximal motif is such a representative motif that is not properly contained in any larger motifs with the same location lists. Although the enumeration problem for maximal motifs with wild cards has been studied in Parida et al. (2001), Pisanti et al. (2003) and Pelfrêne et al. (2003), its output-polynomial time computability has been still open. The main result of this paper is a polynomial space polynomial delay algorithm for the maximal motif enumeration problem for the repeated motifs with wild cards. This algorithm enumerates all maximal motifs in an input string of length n in O(n ³) time per motif with O(n) space, in particular O(n ³) delay. The key of the algorithm is depth-first search on a tree-shaped search route over all maximal motifs based on a technique called prefix-preserving closure extension. We also show an exponential lower bound and a succinctness result on the number of maximal motifs, which indicate the limit of a straightforward approach. The results of the computational experiments show that our algorithm can be applicable to huge string data such as genome data in practice, and does not take large additional computational cost compared to usual frequent motif mining algorithms. This work is done during the Hiroki Arimura’s visit in LIRIS, University Claude-Bernard Lyon 1, France.     

The heterogeneous impact of pension income on elderly living arrangements: evidence from China’s new rural pension scheme

This paper investigates the impact of pension income on living arrangements of the elderly. Taking advantage of a unique opportunity due to the recent establishment and expansion of the New Rural Pension Scheme in China, we explicitly address the endogeneity of pension status and pension income through a fixed-effect model with instrumental variable approach by exploiting exogenous time variation in the program implementation at county level. We find an overall positive effect of pension income on independent living as well as considerable heterogeneity. The positive income effects of the NRPS are concentrated among the elderly with adult children living nearby, of higher socio-economic status, and with better health at baseline; for other groups, the effects are insignificant. We also find that more generous programs exhibit larger effects. Our results highlight that living arrangement is multidimensional in rural China.     

Does It Matter How We Assess Standard of Living? Evidence from Indian Slums Comparing Monetary and Multidimensional Approaches

As part of Sustainable Development Goals, the United Nations have set targets of upgrading slums and reducing poverty in all its dimensions by 2030. Policies towards improving the living conditions of slum-dwellers require proper assessment of their standard of living as well as understanding the associated characteristics. In this paper, using slum-level primary household survey data from three largest Indian cities, we, first, assess the standard of living of slum dwellers using both monetary and non-monetary approaches and then explore how various household and spatial characteristics are consistently or differently associated with both forms of assessments. We use standard monetary indicators, but to assess non-monetary standard of living, use a counting approach framework and justify the selection of specific indicators in the context of slums. Our analysis yields some interesting observations as some characteristics are differently associated with monetary and non-monetary living standards, which should affect policy designs in slums.     

Estimating a sensitive proportion through randomized response procedures based on auxiliary information

Randomized response techniques are widely employed in surveys dealing with sensitive questions to ensure interviewee anonymity and reduce nonrespondents rates and biased responses. Since Warner’s (J Am Stat Assoc 60:63–69, 1965) pioneering work, many ingenious devices have been suggested to increase respondent’s privacy protection and to better estimate the proportion of people, π _A , bearing a sensitive attribute. In spite of the massive use of auxiliary information in the estimation of non-sensitive parameters, very few attempts have been made to improve randomization strategy performance when auxiliary variables are available. Moving from Zaizai’s (Model Assist Stat Appl 1:125–130, 2006) recent work, in this paper we provide a class of estimators for π _A , for a generic randomization scheme, when the mean of a supplementary non-sensitive variable is known. The minimum attainable variance bound of the class is obtained and the best estimator is also identified. We prove that the best estimator acts as a regression-type estimator which is at least as efficient as the corresponding estimator evaluated without allowing for the auxiliary variable. The general results are then applied to Warner and Simmons’ model.     

College Students' Money Beliefs and Behaviors: An Asian Perspective

The multidimensionality of money was investigated, using exploratory factor analysis (EFA). The respondents, 290 college students from Korea, Japan, and the United States, were administered a survey, which included socio-demographic questions, and Furnham's (1984) Money Beliefs and Behaviors (MBBS) Scale. Through a series of principal components analyses, a three-factor model with 10 MBBS items was identified. The three factors, Power, Security, and Financial Modesty accounted for 53.6% of the variance. The findings have implications for college students and financial management practitioners.     

Citizens’ Perception of Past Environmental Damage and Liability in Countries with Transition: Evidence from Kemerovo,Russia

This paper analyzes citizens’ perception of past environmental damage and liability through the estimation of willingness to pay for the implementation of decontamination and land rehabilitation of the damaged site. The paper takes the Russian Federation as a case of country in transition and focuses on Kemerovo region as one of the most affected regions in the country. The major analytical tool employed in the study is choice experiment, data for which was collected through a household survey. Primary conclusion of the analysis is that citizens' willingness to financially support the implementation of environmental quality improvement projects is not high though individuals in the studied area express high level of concern over the issue in focus.