Modelling Illegal Drug Participation

Abstract

Summary. We contribute to the small, but important, literature exploring the incidence and implications of misreporting in survey data. Specifically, when modelling 'social bads', such as illegal drug consumption, researchers are often faced with exceptionally low reported participation rates. We propose a modelling framework where firstly an individual decides whether to participate or not and, secondly, for participants there is a subsequent decision to misreport or not. We explore misreporting in the context of the consumption of a system of drugs and specify a multivariate inflated probit model. Compared with observed participation rates of 12.2%, 3.2% and 1.3% (for use of marijuana, speed and cocaine respectively) the true participation rates are estimated to be almost double for marijuana (23%), and more than double for speed (8%) and cocaine (5%). The estimated chances that a user would misreport their participation is a staggering 65% for a hard drug like cocaine, and still about 31% and 17%, for the softer drugs of marijuana and speed.

Mental health, reporting bias and economic transitions

“…In a similar context, Brown et al (2018) consider the modelling of illicit drug participation. There, the basic hypothesis is that, due to very similar reasons to those considered in the current paper, a subset of true illicit drug participants, will actually mis-report their true behaviour.…”

Early Illicit Drug Use and The Age of Onset of Homelessness

“…Nor can we entirely rule out systematic under‐reporting of drug use of the kind that was discussed by Brown et al . (), although only 20% (52%) of the wave 1 sample reported never having used cannabis (illegal drugs other than cannabis).…”

“…Again we cannot rule out recall error in the reported age at which the individual first engaged in these behaviours. Nor can we entirely rule out systematic under-reporting of drug use of the kind that was discussed by Brown et al (2018), although only 20% (52%) of the wave 1 sample reported never having used cannabis (illegal drugs other than cannabis).…”

Pharmaceutical drug misuse: are industry of employment and occupation risk factors?

“…In terms of the other control variables, we follow the existing literature (e.g. Cameron and Williams, ; Ramful and Zhao, ; Brown et al ., ) and include the following: gender; age; whether the individual is of Aboriginal or Torres Strait Islander descent; whether the individual resides in a capital city; is married or cohabiting; comes from a single‐parent household; whether or not there are preschool‐aged children in the household; educational attainment distinguishing between four categories of highest educational attainment as follows: a tertiary degree, a non‐tertiary diploma or trade certificate, year 12 education and less than year 12 education, which is the omitted category; the natural logarithm of real personal annual income before tax measured in Australian dollars and the individual's main labour market status. Finally, for our analysis of the sample of employed individuals, we focus on industry and occupation effects; the classifications, based on the Australian and New Zealand Standard Industrial Classification and the Australian and New Zealand Standard Classification of Occupations, are detailed in the following section.…”