Int. J. Environ. Res. Public Health 2011, 8 1674 other compensatory behaviors has been somewhat limited. Based on previous literature, smokers faced with higher cigarette prices may seek out cheaper tobacco outlets [6,21,22], may find tax-free or tax- reduced sources [4,6,21], may shift to lower cost forms of tobacco such as cheaper brands or roll-your- own tobacco [6,21,22], or they may choose to purchase tobacco products in bulk or in cartons [21,22]. Previous literature using data from the International Tobacco Control (ITC) study did not find an overall effect of reduced cessation with use of low or untaxed sources. However, those who used these sources were approximately 30% less likely to report making quit attempts [7]. A study from the United States found that use of discount brands was associated with about a 20% reduction in cessation at follow-up [23]. However, these studies have not assessed the use of price minimizing behaviors and the effect on cessation by individuals in various socio-economic groups. Given the known relationship between SES and smoking, the relationship between SES and use of price minimizing behaviors [24], and the differences in price responsiveness of lower SES smokers, SES may be an important modifier on the impact of price minimizing behaviors and cessation outcomes. Access to cheaper tobacco sources, such as discount/generic brands, low/untaxed sources, or bulk purchasing, can undermine the effects of price increases because they allow for alternative options instead of quitting or cutting down. The possible modifying role of SES on this relationship is important, but few studies have examined socio-economic differences in compensatory behaviors aimed at alleviating the burden of increasing cigarette prices and their impact on smoking cessation outcomes. This information may be especially useful in directing future public health policies. This paper examines how price minimizing behaviors impact efforts to stop smoking and remain off cigarettes. Additionally, it assesses how SES modifies the relationship between use of lower priced tobacco products and cessation behaviors. 2. Experimental Section 2.1. Data Source Data analyzed from this study come from several survey waves of the International Tobacco Control (ITC) Policy Evaluation Project-Four Country Survey (ITC-4 Survey). The conceptual framework and methodology of this project have been published in full elsewhere [25,26]. Briefly, the objective of the ITC-4 Project is to evaluate the psychosocial and behavioral effects of the goals and interventions set forth in the Framework Convention on Tobacco Control (FCTC) [25]. The ITC Study has both cross-sectional and longitudinal study arms. Following a ―quasi-experimental‖ study design, researchers can evaluate the effectiveness of tobacco control policies by following and comparing both between and within country trends occurring after implementation [25]. The ITC-4 survey consists of parallel prospective surveys which follow a nationally representative cohort of adult smokers in the four largest English-speaking countries: the United States (US), Canada (CA), the United Kingdom (UK), and Australia (AU). Participants were identified using stratified random digit dialing and interviews were conducted using computer assisted telephone interview (CATI) software at multiple research facilities. A complex sampling design, incorporating population stratification, unequal probabilities of selection, and random digit dialing techniques, is used to gain a representative sample from each country [26]. Interviews were conducted in both English and French,