Optimal design of sin taxes in the presence of nontaxable sin goods

Sin good consumption entails health damage, which is in general not fully perceived by individuals, what results in its overconsumption. One way to tackle this problem is to tax these unhealthy goods. However, not all the individual choices that affect health status can be easily observed and effectively taxed by the government. This paper considers a setting where individuals can consume two types of sin goods that differ in their observability (taxability) by the government. As a benchmark, the first‐best taxes for the observable and non‐observable sin good are derived, considering homogeneous individuals. In the second‐best setting, where observability on sin good consumption is limited, the rule for the taxable sin good is shown to depend on the degree of complementarity or substitutability with the unobservable sin good. Finally, redistributional considerations are incorporated by extending the analysis to a setting where individuals differ in their wealth and in their degree of misperception of the health damage caused by sin good consumption. Policy implications are illustrated considering physical inactivity and illicit drugs as examples of non‐taxable sin goods, while alcohol, tobacco, fat and sugar account for the taxable sin goods