Health, social and economic impacts of the UK Treasury Soft Drinks Industry Levy: a synopsis of a systems-thinking informed multi-method evaluation

Background In March 2016, a tiered tax was announced on industries manufacturing or importing sugar-sweetened beverages in the United Kingdom. The Soft Drinks Industry Levy was implemented in April 2018 with two tiers: £0.18/l on drinks containing ≥ 5 g/100 ml and < 8 g/100 ml of added sugar, £0.24/l on drinks containing ≥ 8 g/100 ml of added sugar, with no levy on drinks containing < 5 g/100 ml of added sugar. The Soft Drinks Industry Levy is a complex intervention that acts as a disruptor in the commercial food system. As such, it demanded an evaluation that went beyond a narrow focus on a single outcome to incorporate assessment of a range of theorised intervention effects and their dynamic inter-relationships, taking a ‘systems’ perspective. Objectives We undertook formative work over 6 months to underpin the evaluation, leading to five work packages, which aimed to evaluate: Work package 1: impacts on formulation, marketing, prices, purchases and consumption of sugar-sweetened beverages, and early health impacts. Work package 2: estimated impacts on medium- to long-term health outcomes. Work package 3: estimated economic impacts on food and other industries, His Majesty’s Treasury, health and social care systems. Work package 4: impacts on key stakeholders: the public, policy-makers and industry. Work package 5: the wider implications of the Soft Drinks Industry Levy in a synthesis of all findings and other evaluations. Methods Work package 1 adopted a natural experimental evaluation design and used quantitative methods, including interrupted time series analysis. Work package 2 employed epidemiological modelling to simulate longer-term health outcomes. Work package 3 used micro- and macroeconomic modelling to estimate the net costs and benefits of the Soft Drinks Industry Levy and to simulate longer-term economic outcomes. Work package 4 used qualitative methods to explore acceptability and impacts of the Soft Drinks Industry Levy for diverse stakeholders. Work package 5 synthesised findings from this and other evaluations of the Soft Drinks Industry Levy and identified implications for policy and further research. Results Our evaluation shows that the Soft Drinks Industry Levy: incentivised reduction in sugar purchased in soft drinks and in food and drinks overall; was associated with reduced inequalities in sugar purchased from soft drinks, with a 1.6% point reduction in prevalence of obesity in Year 6 girls, and with a 12% reduction in hospital admissions for carious tooth extractions in children and adolescents up to 18 years; was viewed favourably by policy-makers and the public; and did not have lasting negative impacts on the economic performance of soft drinks companies. Based on changes in sugar consumption observed, epidemiological modelling suggested that the Soft Drinks Industry Levy will lead to health gains and to net monetary benefit to the health sector, as well as to reductions in health inequalities. The Soft Drinks Industry Levy was forecast to produce a 0.004% cumulative gross domestic product loss to the United Kingdom economy over a 22-year period. Nevertheless, the Soft Drinks Industry Levy represents good value for money when balancing the overall health benefits against the economic impacts. The results of this evaluation are consistent with the results of studies undertaken by others. Limitations There were limitations of all the studies we undertook, which are detailed in each of the 18 publications referenced in this report. Since we commenced this research, newer methods have become available for evaluations of interventions in complex adaptive systems. We have taken a narrative approach to triangulating and synthesising findings from our diverse range of studies. The use of more formal methods, such as contribution analysis or process tracing, may have strengthened causal inference. Future work Government is strengthening the Soft Drinks Industry Levy, by reducing the lower levy threshold to 4.5 mg of sugar per 100 ml of soft drink, increasing the levy rates over time in line with inflation, and including milk-based drinks, and the benefits of such changes should, when implemented, be evaluated. The principles underlying the Soft Drinks Industry Levy could be applied to similar levies on other unhealthy foods, and the benefits of these also need to be modelled. Meanwhile, the longer-term impacts of the Soft Drinks Industry Levy, including industry adaptations, should be monitored, including its impacts on the sugar and soft drinks markets in the United Kingdom and globally. Further research is also needed on the implications of rising levels on non-sugar sweeteners in soft drinks and on ways to reduce the sweetness of all foods. Conclusions The Soft Drinks Industry Levy was a novel, tiered sugar-sweetened beverage tax that incentivised industry reformulation to remove sugar from soft drinks. It was effective in incentivising reformulation and was associated with observed and projected future health benefits. Although it is estimated that the Soft Drinks Industry Levy had costs for the United Kingdom economy, these were mitigated by benefits for the public, the National Health Service and other sectors. The Soft Drinks Industry Levy has been positively received by the public, policy-makers and, to an extent, industry, and offers a model for future fiscal food policy in the United Kingdom and internationally. Funding This synopsis presents independent research funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme as award number 16/130/01.