Keeping off the Grass? An Econometric Model of Cannabis Consumption by Young People in Britain

This paper presents estimates of a dynamic individual-level model of cannabis consumption, using data from a 1998 survey of young people in Britain. The econometric model is a split-population generalisation of the non-stationary Poisson process, allowing for a separate dynamic process for initiation into cannabis use. The model allows for heterogeneity in consumption levels and behavioural shifts induced by leaving education and the parental home.Cannabis; Illicit drugs; Transition modelling; Poisson processes; Demand analysis

Estimation of dynamic linear models in short panels with ordinal observation

We develop a simulated ML method for short-panel estimation of one or more dynamic linear equations, where the dependent variables are only partially observed through ordinal scales. We argue that this latent autoregression (LAR) model is often more appropriate than the usual state-dependence (SD) probit model for attitudinal and interval variables. We propose a score test for assisting in the treatment of initial conditions and a new simulation approach to calculate the required partial derivative matrices. An illustrative application to a model of households' perceptions of their financial well-being demonstrates the superior fit of the LAR model.Dynamic panel data models, ordinal variables, simulated maximum likelihood, GHK simulator, BHPS

The Use of Self-Report and Drugs Tests in the Measurement of Illicit Drug Consumpiton

We use data from the New England and Wales Arrestee Drug Abuse Monitoring (NEW-ADAM) programme to assess the validity of self-report measures of illicit drug use and to evaluate the use of alternative drug testing strategies within survey enquiries. Our analysis of the NEW-ADAM data reveals that bio-assay measurements of drug use tend not to be very sensitive to the cut-off levels selected for screening tests, a result that holds for cannabis, cocaine and opiates. We also show that a self-reported history of previous drug use can be used as a way of identifying individuals who are potential under-reporters of current drug use. This suggests a selective drug testing strategy which can reduce dramatically the cost of drug testing without comprising the accuracy of measurements of illicit drug use.Drugs testing; Self-reports; Concordance; Testing Strategies