Survey methods were the same in all years. The basic design was a stratified two-stage probability sample, with schools selected at the first stage and students at new post the second. Schools were randomly sampled from each Australian State and Territory and the three main education sectors to ensure proportional representation. Principals of selected schools gave permission to conduct the survey. If a school refused, it was replaced by the school nearest to it within the same education sector. Schools provided students from either Year levels 7�C10 (age range: 12�C15) or Year level 11 and 12 (age range: 16�C17). A total of 80 students were randomly selected from each school. Approximately 0.1% of selected students actively declined to participate.

Adult Smoking Data from 1980 to 1998 were taken from the triennial Australian Smoking and Health Surveys (SHS; Hill, White, & Scollo, 1998; Hill, White, & Segan, 1995). Data were collected as part of an omnibus face-to-face survey conducted by a market research company, using the same sampling and interviewing procedures each wave. Sampling was conducted at the Australian Bureau of Statistics census collector��s district (CDs) level. CDs were selected at random within specified strata that included state and rural/urban divisions. Within each CD, an individual residence was chosen at random for the first contact, with the adjacent house contacted next. Further adjacent households were approached until the required number of interviews for that CD was obtained (usually 8).

Once contact with a household was established, one person aged 14 years or older was randomly selected for interviewing using the next/last birthday method. If the selected person was not available for interview, three call backs were made. This survey was discontinued after 1998. From 2002 onwards, we have data from the International Tobacco Control (ITC) Policy Evaluation Survey��Australian arm. This is a panel or cohort survey with replenishment from the same sampling frame. It uses computer-assisted telephone interviews on an approximately annual schedule. We used data collected in the first wave in 2002, followed by the fourth (2005) and seventh (2008) waves. Respondents are selected via random digit dialing to ensure a broadly representative sample. All respondents were smokers at the time of recruitment (having smoked at least 100 cigarettes in their lifetime and having smoked at least once in the past 30 days).

At each wave, the sample is replenished using the same sampling frame to maintain its size. (Retention rates between waves exceed 70%). A detailed description of the conceptual framework of the ITC project (Fong et al., 2006) and its methodology (Thompson et al., GSK-3 2006) can be found elsewhere. Respondents were included only if they were current smokers (daily, weekly, or monthly). Details of the samples used can be found in Table 1.