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

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.