S. and Canadian data produced estimates similar to those presented following website above and are available on request. All models we also estimated with an interaction term between sociodemographic variables (age, gender, income, and education) and price measures to investigate a difference in responsiveness among population subgroups. Generally, interactions were not found to be statistically significant. The exception was moderate income that increased the impact of price in all models. This means that smokers with moderate incomes were more responsive to price changes than those with low or high incomes. The inclusion of the interaction terms did not statistically alter the results of the regressions. These analyses are available on request.

Discussion The ITC data confirmed that cigarette prices were lowest in the United States relative to Australia, Canada, and the United Kingdom even after adjusting for the purchasing power parity of various currencies. In addition, U.S. smokers were exposed to more price promotions than those in the other three countries. Consequently, a higher percentage of U.S. smokers reported that they would find a cheaper source of their favorite brand and a lower percentage of them expect to quit in response to a hypothetical increase in cigarette price compared with smokers in Australia, Canada, and the United Kingdom. Nevertheless, anticipated higher cigarette prices increase the probability of adult smokers�� contemplating quitting and/or lower cigarette use in all four countries, with stronger impact in Australia and Canada.

The magnitude of a future price increase seems to be more important in promoting intention to quit and/or cutback on smoking than the general level of cigarette prices in the area where a smoker lives. Comparing only U.S. and Canadian smokers confirmed that Canadian smokers are more likely to expect to quit and/or to smoke fewer cigarettes, that is, to expect behavior changes that lead to better health. Given that U.S. smokers are more exposed to various price promotions at the point of sale, it might be easier for them to avoid a price increase by obtaining cigarettes from cheaper sources. Since there is a greater diversity of cigarette prices in the United States compared with Canada and the U.S. multitiered pricing has been in place longer than in Canada, U.S. smokers may be also more willing to switch their brands to accommodate the higher cigarette prices. This study makes several contributions to existing literature. It is the first academic study to employ a hypothetical increase in price to analyze expected cessation among adult smokers, though a similar study has been conducted among adolescents (Ross GSK-3 et al., 2005).