Economic Evaluations of Obesity Targeted Sugar-Sweetened Beverages (SSB) Taxes - A Systematic Review to Identify Methodological Issues

Introduction: Taxes on sugar-sweetened beverages (SSB) have been proposed as an effective measure to tackle obesity and obesity-related health issues. The long-term consequences of SSB taxes have been modelled using economic evaluations. However, reviews of economic evaluations of public health interventions in other contexts have raised several methodological challenges, and these issues have not been explored in respect to a SSB tax.Methods: A systematic review was conducted to appraise economic evaluations of a tax on SSB. The literature search was performed in February 2021 for EconLit, Business Source Complete, Medline, and CINAHL. Criteria for assessing studies were developed to align with previously identified methodological issues in economic evaluations of public health interventions and key issues in the evidence for SSB taxes. These include measuring effects, valuing outcomes, assessing costs, and engaging equity.Results: Fourteen economic evaluations of a tax on SSB were identified. A tax on SSB was found to be cost saving and may reduce health inequity. There were technical issues regarding the approaches used to estimate the effects. In particular, there was uncertainty in estimating the impact of SSB consumption and SSB taxes on body weight. There was also uncertainty in valuing the substitution effect where SSB consumers could switch to other similar products. In addition, the evaluations were limited in terms of the information presented. Consideration of non-health consequences both in term of costs and outcomes in the evaluations was not common. More than half of the evaluations provided equity analyses but most of these used informal approaches such as subgroup analyses to inform equity outcomes of the tax.Conclusion: Methodological issues were identified in current economic evaluations examining the impact of a tax on SSB. Greater transparency of the full details of the evidence and robust analyses is needed for future evaluations