Impact of taxes in Tonga targeting foods high in fat, salt and sugar: interrupted time series analyses
Andrea M. Teng, Viliami Puloka, Alice Hyun Min Kim, Selai Tukunga, Faleola Mafi, Karen Fukofuka, Nick WilsonAbstract
Objective:
Sugar-sweetened beverage taxes have been widely evaluated; however, less is known about the effects of taxes on unhealthy foods. This study examines the effects of Tonga’s food taxes on food prices and import volumes.
Design:
Interrupted time series analysis using segmented linear regression was used to evaluate tax impacts on both retail prices and import volumes of taxed foods. Observed post-tax trends were compared with a counterfactual. The counterfactual was the projected pre-tax trends, with adjustment for autocorrelation and changes in GDP, tourism, season, exchange rates and oil prices over time. Random effects meta-analysis was used to summarise outcomes across food types.
Setting:
Nine Tongan food tax increases were examined, varying from US$0·17/kg to US$1·08/kg, and averaging 28 % of import value.
Results:
In the first-year post-tax, retail prices increased for ten of eleven taxed foods, with an average increase of 13 % (95 %CI: 5 % to 21 %). Price increases for chicken pieces (46 % and 39 %), mutton flaps (20 %), corned beef (20 %), ice cream (11 %), salted beef (6 %) and mayonnaise (3 %) were statistically significant. Import volumes decreased for eight of nine taxed foods with a mean decrease of 41 % (95 %CI: 17 % to 58 %). Import decreases for sausages (68 %) and ice cream (72 %) were significant.
Conclusions:
Consistent with economic theory, excise taxes on unhealthy foods in Tonga were associated with increases in retail prices and decreased imports of taxed foods. These findings add to the limited evidence base that excise taxes on unhealthy foods can effectively raise prices and reduce supply.