Impact of a sugar-sweetened beverage tax two-year post-tax implementation in Seattle, Washington, United States.

This study examines longer-run impacts of the Seattle, Washington, Sweetened Beverage Tax (SBT) on beverage prices, volume sold, and cross-border shopping. We use a difference-in-differences estimation approach, drawing on universal product code-level store scanner data on taxed and untaxed beverages one-year pre-tax and two-year post-tax with Portland, Oregon, as the comparison site. Two-year post-tax, prices of taxed beverages increased by 1.04 cents per ounce (59% tax pass-through rate). Volume sold of taxed beverages fell by 22%. Declines were larger for family-size (29%) compared to individual-size (10%) beverages; particularly for soda (36% decrease for family-size compared to no change for individual-size). We found no change in volume sold of taxed beverages in Seattle's 2-mile border area, suggesting no cross-border shopping. Overall, we found a sustained impact of the Seattle SBT two-year post-tax implementation suggesting that sugar-sweetened beverage taxes may yield permanent reductions in demand for sugary beverages and associated health harms.