Sampling Procedure
The sampling began with urban and rural stratification, followed by the selection of primary sampling units (census units in urban strata and villages in rural strata) proportional to population size. Secondary sampling units (households) were then selected using the 'random step method'. If no smokers resided in the selected household, a short general survey was administered to the first adult person answering the door. If the household had a smoker, all smokers were listed and one was randomly selected for the interview. If the selected respondent refused or was not home during any of the three interview attempts, another smoking resident was selected. If no smoking residents were available for interview, the household was recorded as 'non-responding' and the interviewer walked past five households on average (the number varied slightly for urban and rural strata) and selected a replacement household.
Surveyors completed 2997 interviews in wave 1. Of those, 1765 people were successfully re-interviewed in wave 2. These were supplemented with new households (also selected using the 'random step method') which brought the total people interviewed in wave 2 to 3040. In wave 3, there were 1578 people interviewed in both waves 1 and 2 (our panel), 240 people interviewed in wave 1 but not in wave 2, 1036 people only interviewed in wave 2, and 335 people added in wave 3 for the first time. As such, there were 3189 people interviewed in wave 3. For quality control, an independent controller crosschecked a randomly selected 10% of completed interviews in each wave and no major errors were identified.
Response Rate
The total attrition in our panel was 52.6% with attrition varying significantly by region. The highest rate was in Tbilisi (62.7%) followed by Kutaisi (52.2%), Akhaltsikhe (47.4%), Gori (31.9%) and Zugdidi (27.4%). Within each region, there was no significant difference in the likelihood of attrition by gender, employment, the probability of showing a pack or the probability of owning an illicit pack. Given the attrition patterns, the analysis was done by region wherever possible.