Sustained Impact of the Philadelphia Beverage Tax on Beverage Prices and Sales Over 2 Years.

INTRODUCTION: It is unclear whether changes in beverage price and sales after beverage tax implementation can be sustained long term. This study aims to quantify the changes in beverage prices and sales in large retailers 2 years after the implementation of the 1.5 cents per ounce Philadelphia beverage tax. METHODS: Data on price and volume sales of beverages and potential food substitutes were collected from 109 supermarkets, 45 mass merchandizers, and 350 pharmacies in Philadelphia, Baltimore (control), and Pennsylvania ZIP codes bordering Philadelphia (to investigate potential cross-border shopping for tax avoidance). Difference-in-differences analyses compared beverage prices and volume sales in the year before tax implementation (2016) to 2 years after (2018). Data were analyzed in 2020-2021. RESULTS: Difference-in-differences analyses found that after tax implementation, taxed beverage prices in Philadelphia increased by 1.02 cents per ounce (95% CI=0.94, 1.11; 68% pass through), and taxed beverage volume sales in stores decreased by 50% (95% CI=36%, 61%). After accounting for cross-border shopping, taxed beverage volume sales decreased in Philadelphia by 35% in 2018. Volume sales of nontaxed beverages did not change after tax implementation (difference-in-differences=4%, 95% CI= -3%, 12%). Volume sales of nontaxed beverage concentrates increased on average by 34% (95% CI=19%, 51%), but there was no evidence of substitution to high-calorie foods. CONCLUSIONS: There was a large reduction in taxed beverage volume sales 2 years after Philadelphia tax implementation, even after accounting for cross-border shopping. Increases in nontaxed beverage concentrate sales likely partially offset this decline, but there was no evidence of post-tax food substitution.