The Impact of Seattle's Sugar-Sweetened Beverage Tax on Substitution to Sweets and Salty Snacks.

ABSTRACT

BACKGROUND: Sugar-sweetened beverage (SSB) taxes may have broad effects on purchases of untaxed foods, and substitution of SSBs with untaxed sweets and/or salty snacks could offset the intended dietary and health effects of these policies. OBJECTIVES: To test whether there were changes in sales and calories sold for untaxed foods in response to the SSB tax in Seattle, Washington, at 12 and 24 months post-tax implementation. METHODS: On 1 January 2018, the City of Seattle levied a 1.75 cents per ounce excise tax on distributors selling targeted SSBs. We utilized universal product code-level store scanner data and employed a difference-in-differences approach to assess the impacts of the tax on the changes in 1) sales of sweets and salty snacks; and 2) total calories sold for sweets in Seattle relative to changes in its comparison site of Portland, Oregon, at 12 and 24 months post-tax. RESULTS: In the 12 months post-tax, sales of sweets increased by 4% [ratio of incidence rate ratios (RIRR), 1.04; 95% CI, 1.03-1.05] in Seattle relative to the changes in Portland; at 24 months post-tax, sweet sales increased by 6% (RIRR, 1.06; 95% CI, 1.05-1.07) relative to the pretax period. There was no significant change in sales of salty snacks at 12 months (RIRR, 1.00; 95% CI, 0.99-1.01) or 24 months (RIRR, 1.00; 95% CI, 0.98-1.02) post-tax. Total calories sold for sweets increased by 3% (RIRR, 1.03; 95% CI, 1.02-1.05) in Seattle compared with Portland at 12 months post-tax and by 4% (RIRR, 1.04; 95% CI, 1.02-1.05) at 24 months after implementation. CONCLUSIONS: There was modest substitution of SSBs for sweets in Seattle following tax implementation. However, this increase in sales and calories sold is not likely to offset previously identified tax-related reductions in the demand for taxed beverages in Seattle. Thus, SSB taxes are a promising policy tool to reduce caloric intake in the United States.