Why Affordability? Cigarette affordability analysis is an important input to guide tobacco control policy, in particular tobacco taxation. Global evidence shows that when cigarettes are made substantially less affordable for consumers, many people will quit or reduce smoking, despite the addictive power of nicotine, while many who would have smoked will never start. This study investigates trends in cigarette affordability in Indonesia from 2002 to 2017. Affordability analysis is critical for Indonesia today, because the government has accelerated tobacco control measures, notably by raising the country's cigarette excise tax six times between 2011 and 2017. Affordability is key to understanding these measures' successes and shortfalls, and to honing future strategies that can build on the momentum achieved. Background: Indonesia's Tobacco Epidemic Health impacts. Estimated at 68.1 percent in 2016, Indonesia's male smoking prevalence is among the highest in the world. The country's five leading causes of death are all tobaccorelated, including ischemic heart disease, cerebrovascular disease, tuberculosis, diabetes, and chronic respiratory diseases (IHME, 2017). Morbidity from smoking-related diseases accounts for more than 21 percent of all cases of chronic disease in Indonesia. Economic damage. Along with its health impacts, tobacco consumption imposes a heavy economic burden, primarily on Indonesia's poor, who risk lost income, reduced labor productivity, and deeper impoverishment from out-of-pocket payments for the treatment of tobacco-related diseases. While the poor suffer most, all of Indonesian society is affected by the tobacco epidemic. Tobacco-related diseases increasingly burden the country's national health insurance program. Indonesia's smoking-attributable health expenditure is estimated at some US$ 1.2 billion per year (Barber et al., 2008; Goodchild et al., 2017), equivalent to about 8 percent of Indonesia's total public expenditure on health (World Bank, 2016). Direct and indirect costs of tobacco-related disease divert resources needed for Indonesia's development-posing a growing challenge to the country. Harm to children. In 2013, 56 percent of Indonesian children aged 0-4 years were exposed to secondhand smoke in their homes (IAKMI, 2014). Paternal smoking predicts an increased probability of short-term and chronic malnutrition among Indonesian children