Philadelphia Beverage Tax and Association With Prices, Purchasing, and Individual-Level Substitution in a National Pharmacy Chain.

Importance: Taxes on sweetened beverages are being implemented around the globe; an understanding of these taxes on individual-level behavior is necessary. Objective: To evaluate the degree to which the sweetened beverage tax in Philadelphia, Pennsylvania, was associated with changes in beverage prices and individual-level purchasing over time at a national pharmacy chain in Philadelphia compared with Baltimore, Maryland. Design, Setting, and Participants: Using a difference-in-differences approach and generalized linear mixed models, this cohort study examined beverage purchases made by loyalty cardholders at a national chain pharmacy retailer with stores in Philadelphia and Baltimore (control city) from before tax to after tax. Beverage sales (in US dollars) were linked by unique loyalty card numbers to enable longitudinal analyses. Data were collected from January 1, 2015, through December 31, 2017 (2 years before tax and 1 year after tax); data analyses were conducted from January through October 2022. Exposure: Implementation of Philadelphia's 1.5 cents/oz tax on sweetened beverages. Main Outcomes and Measures: The outcomes were the change in mean beverage price per-ounce and mean beverage volume purchased per cardholder transaction. Individual-level point-of-sale scanner data from all beverage purchases were analyzed. Results: A total of 1188 unique beverages were purchased from the same stores before tax and after tax. There were 231 065 unique cardholders in Philadelphia and 82 517 in Baltimore. Mean prices of taxed beverages (n = 2 094 220) increased by 1.6 (95% CI, 1.3-2.0) cents/oz (106.7% pass-through) in Philadelphia compared with Baltimore from before tax to after tax. Philadelphia cardholders purchased 7.8% (95% CI -8.1% to -7.5%) fewer ounces of taxed beverages and 1.1% (95% CI, 0.6%-1.7%) more ounces of nontaxed beverages per transaction. Taxed beverages made up a smaller percentage of cardholders' overall beverage purchases after tax (-13.4% [95% CI, -14.2% to -12.6%]), while nontaxed beverages made up a larger share (9.3% [95% CI, 7.7%-10.7%]). Conclusions and Relevance: In this longitudinal cohort study of the Philadelphia beverage tax, the tax was completely passed through to prices and was associated with a 7.8% decline in ounces of taxed beverages purchased at a national pharmacy chain.