Abstract
The Pacific is facing a non-communicable disease (NCD) crisis driven by globalisation and trade, and in part by increased consumption of nutrient-poor energy-dense processed foods. Several jurisdictions in the region have introduced sugar-sweetened beverage (SSB) taxes with stated health goals. However, there are few reviews or evaluations of these policies and the potential health impacts remain unclear. The aim of this thesis was to evaluate the impact of SSB taxes in the Pacific from a public health perspective. Objectives were to: (1) summarise the international evidence from natural experiment studies and assess the average impacts of SSB taxes on purchasing and dietary consumption by meta-analysis; (2) identify and characterise the changes in SSB taxes from 2000-2019 in Pacific jurisdictions; (3) evaluate the impact of SSB tax changes in Tonga (in 2013, 2016 and 2017) and the Cook Islands (in 2008, 2012 and 2014) on price and imports; also manufacturing (Tonga, 2016), sales (Cook Islands, 2014), and how expenditure changes differ by household income (Tonga, 2013). Systematic review, meta-analysis and natural experiment studies, namely interrupted time series analyses and a before and after study of household expenditure, were carried out.
There was clear evidence on systematic review and meta-analysis of the international literature, that SSB taxes reduced purchasing or dietary consumption of taxed beverages, with a 10% reduction (95%CI: 5.0% to 14.7%) for an 10% equivalent SSB tax. There was a small non-significant substitution to untaxed beverages such as water. Heterogeneity of findings between jurisdictions suggested that tax design and contextual factors may have influenced the extent of tax effects.
Widespread use of SSB taxes in the Pacific was identified by a comprehensive review of SSB tax legislation. Three-quarters of Pacific jurisdictions had a SSB tax and more than a third of jurisdictions had increased SSB taxes by more than 20%, while several jurisdictions had also decreased taxes. There were some excellent examples of SSB tax design such as the 2017 tiered volumetric tax in Tonga that targeted a range of SSB categories. The majority of countries had taxes that favoured locally-manufactured beverages; most taxes were ad valorem or volumetric; only two taxes included sugar-sweetened fruit juices and earmarking was rare.
Interrupted time series analysis in Tonga found that all three excise tax increases were associated with increases in soft drink price (of an indicator product) and decreases in taxed beverage import volumes, compared to a counterfactual (and the majority were statistically significant). Manufacturing of bottled water and soft drinks also increased after the tax increase. Soft drink manufacturing increases, however, were dwarfed by the decrease in import volumes.
There was a significant decline in per-capita soft drink expenditure spanning the 2013 Tonga excise, and the decrease was greater in low-income households (although the difference was not statistically significant). Per-capita expenditure on bottled water increased dramatically and the increases were greater in high-income households (not significant).
Tariff increases in the Cook Islands were associated with mixed price changes and relatively small but non-significant declines in taxed beverage import volumes. Contextual changes appeared to have an important influence on study findings such as the revoke of invoice splitting and broad tax changes.
In summary, there is clear and ample evidence that SSB taxes are an effective policy for reducing purchasing and dietary intake of taxed beverages. Although the Pacific is not traditionally looked to for leadership in NCD prevention, there are some excellent examples and widespread use of SSB taxes in the region. SSB taxes in Tonga have likely contributed to a healthier diet, with significant declines in imports and a much smaller corresponding increase in local soft drink manufacturing. Many SSB tax policies could be strengthened to improve health benefits, eg, by equally taxing imported and manufactured SSBs, using volumetric or tiered taxes, targeting the full range of consumed SSBs, adjusting tax levels for inflation, improving home access to safe drinking water, and investing revenue in health and obesity prevention. Natural experiment methods were feasible, valuable and strengthened by a qualitative investigation of contextual data. Further research is needed to understand equity effects. SSB taxes, designed well, are a major tool and one of the most evidence-based prevention measures for addressing NCD risk factors in the Pacific and internationally.