HOME COMPUTERS AND EDUCATIONAL OUTCOMES: EVIDENCE FROM THE NLSY97 and CPS*

Although computers are universal in the classroom, nearly 20 million children in the United States do not have computers in their homes. Surprisingly, only a few previous studies explore the role of home computers in the educational process. Home computers might be very useful for completing school assignments, but they might also represent a distraction for teenagers. We use several identification strategies and panel data from the two main U.S. data sets that include recent information on computer ownership among children—the 2000–2003 Current Population Survey (CPS) Computer and Internet Use Supplements matched to the CPS basic monthly files and the National Longitudinal Survey of Youth 1997 (NLSY97)—to explore the causal relationship between computer ownership and high school graduation and other educational outcomes. Teenagers who have access to home computers are 6–8 percentage points more likely to graduate from high school than teenagers who do not have home computers after controlling for individual, parental, and family characteristics. We generally find evidence of positive relationships between home computers and educational outcomes using several identification strategies, including controlling for typically unobservable home environment and extracurricular activities in the NLSY97, fixed effects models, instrumental variables, and including future computer ownership and falsification tests. Home computers may increase high school graduation by reducing nonproductive activities, such as truancy and crime, among children in addition to making it easier to complete school assignments (JEL I2).     

EFFECTS OF WELFARE REFORM ON ILLICIT DRUG USE OF ADULT WOMEN

Exploiting changes in welfare policy across states and over time and comparing relevant population subgroups within an econometric difference‐in‐differences framework, we estimate the effects of welfare reform on adult women's illicit drug use from 1992 to 2002, the period during which welfare reform unfolded in the United States. The analyses are based on all available and appropriate national data sets, each offering unique strengths and measuring a different drug‐related outcome. We investigate self‐reported illicit drug use (from the National Household Surveys on Drug Abuse and National Surveys on Drug Use and Health), drug‐related prison admissions (from the National Corrections Reporting Program), drug‐related arrests (from Federal Bureau of Investigation Uniform Crime Reports), and drug‐related emergency department episodes (from the Drug Abuse Warning Network). We find robust evidence that welfare reform led to a 10%–21% decline in illicit drug use among women at risk of relying on welfare, as well as associated declines in drug‐related arrests (6%–7%), drug‐related hospital emergency department episodes (7%–11%), and possibly drug‐related prison admissions (11%–19%). The findings indicate that an appropriately designed welfare system with sufficient job opportunities for those who are able to work can result in both increases in employment and decreases in drug use. (JEL I38, K42, J21)     

A decision tree approach for selecting between demand based,reorder, and JIT/kanban methods for material procurement

In designing mechanisms for the procurement of raw materials, a manager is often faced with the task of selecting from a variety of possible methods. Since the performance of these methods is a function of the environment in which they are implemented, it is the responsibility of the manager to select the method best suited for a particular application. In this paper we present a methodology for assisting managers in the selection process. Specifically, three classes of procurement methods are considered, these are: demand based, reorder, and JIT methods. The selection methodology is structured as a decision tree, which considers the annual usage value, lead time ratio, holding cost, vendor location, vendor delivery performance, and material supply value. Each factor is evaluated on a three level scale, and on the basis of these evaluations the tree makes a selection. The application of the methodology is illustrated via some examples.     

INNOVATION STRATEGY AND FINANCIAL PERFORMANCE IN MANUFACTURING COMPANIES: AN EMPIRICAL STUDY

An innovation strategy for the manufacturing function covers four areas: a firm's desired innovation leadership orientation (i.e., being a leader versus being a follower), its level of emphasis on process and product innovation, its use of internal and external sources of innovations, and its intensity of investment in innovation. We examine two models of the association between manufacturing companies' innovation strategy and their financial performance. The first examines the variations in company financial performance as a function of the simultaneous effect of the dimensions of innovation strategy. The second is a sequential model that suggests a causal sequence among the dimensions of innovation strategy that may lead to higher performance. We used data from a sample of 149 manufacturing companies to test the models. The results (1) support the importance of innovation strategy as a determinant of company financial performance, (2) suggest that both models are appropriate for examining the associations between the dimensions of innovation strategy and company performance, and (3) show that the sequential model provides additional insights into the indirect contribution of the individual dimensions of innovation strategy to company performance. Finally, we discuss the implications of these results for managers.     

DETERRENCE,PREEMPTION, AND PANIC: A COMMON‐ENEMY PROBLEM OF TERRORISM

A game‐theoretic analysis of terrorism examines interactions between a terrorist organization and multiple target countries. It considers both preemption and deterrence as counter‐terrorist policies. Damage from terror includes material costs and resultant fear. Fear effects lead to different equilibria and implications for counter‐terrorism policies. The model identifies conditions under which greater preemption may be the rational response to an increase in terrorism, that is, it analyzes the merit of the dictum “offense is the best defense.” It also examines the characteristics of cooperative behavior among target countries in dealing with the threat of terrorism. (JEL C72, D74, F52, F53, H41)     

Graph colouring approach for cell formation problems

This paper presents a graph-theoretic approach for solving the clustering problem in group technology. The machine-component incidence matrix is used to form the weight matrix. Using the two weight matrices, one for the machines and the other for the parts, two graphs are developed. The nodes of each graph are coloured using the proper colouring method. An edge, whose adjacent nodes are of same colour, partitions the graph into subgraphs, thus creating machine-part cells. This cell formation method yields solutions which compare favourably with respect to other available methods. This procedure is illustrated using an example problem from the literature.