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Importance: Policy makers have implemented beverage taxes to generate revenue and reduce consumption of sweetened drinks. In January 2017, Philadelphia, Pennsylvania, became the second US city to implement a beverage excise tax (1.5 cents per ounce). Objectives: To compare changes in beverage prices and sales following the implementation of the tax in Philadelphia compared with Baltimore, Maryland (a control city without a tax) and to assess potential cross-border shopping to avoid the tax in neighboring zip codes. Design, Setting, and Participants: This study used a difference-in-differences approach and analyzed sales data to compare changes between January 1, 2016, before the tax, and December 31, 2017, after the tax. Differences by store type, beverage sweetener status, and beverage size were examined. The commercial retailer sales data included large chain store sales in Philadelphia, Baltimore, and the Pennsylvania zip codes bordering Philadelphia. These data reflect approximately 25% of the ounces of taxed beverages sold in Philadelphia. Exposures: Philadelphia's tax on sugar-sweetened and artificially sweetened beverages. Main Outcomes and Measures: Change in taxed beverage prices and volume sales. Results: A total of 291 stores (54 supermarkets, 20 mass merchandise stores, 217 pharmacies) were analyzed. The mean price per ounce of taxed beverages in Philadelphia increased from 5.43 cents in 2016 to 6.24 cents in 2017 at supermarkets; from 5.28 cents to 6.24 cents at mass merchandise stores, and from 6.60 cents to 8.28 cents at pharmacies. The mean price per ounce in Baltimore increased from 5.33 cents in 2016 to 5.50 cents in 2017 at supermarkets, from 6.34 cents to 6.52 cents at mass merchandise stores, and from 6.76 cents to 6.93 cents at pharmacies. The mean per-ounce difference in price between the 2 cities was 0.65 cents (95% CI, 0.60 cents-0.69 cents; P<.001) at supermarkets; 0.87 cents (95 % CI, 0.72 cents-1.02 cents; P<.001) at mass merchandise stores, and 1.56 cents (95% CI, 1.50 cents-1.62 cents; P<.001) at pharmacies. Total volume sales of taxed beverages in Philadelphia decreased by 1.3 billion ounces (from 2.475 billion to 1.214 billion) or by 51.0% after tax implementation. Volume sales in the Pennsylvania border zip codes, however, increased by 308.2 million ounces (from 713.1 million to 1.021 billion), offsetting the decrease in Philadelphia's volume sales by 24.4%. In Philadelphia, beverage volume sales in ounces per 4-week period between before and after tax periods decreased from 4.85 million to 1.99 million at supermarkets, from 2.98 million to 1.72 million at mass merchandise stores, and from 0.16 million to 0.13 million at pharmacies. In Baltimore, the beverage volume sales in ounces decreased from 2.83 million to 2.81 million at supermarkets, from 1.05 million to 1.00 million at mass merchandise stores, and from 0.14 million to 0.13 million at pharmacies. This was a 58.7% reduction at supermarkets (difference-in-differences, -2.85 million ounces; 95% CI, -4.10 million to -1.60 million ounces; P < .001), 40.4% reduction at mass merchandise stores (difference-in-differences, -1.20 million ounces; 95% CI, -2.04 million to -0.36 million ounces; P = .001), and 12.6% reduction in pharmacies (difference-in-differences, -0.02 million ounces; 95% CI, -0.03 million to -0.01 million ounces; P < .001). Conclusions and Relevance: In Philadelphia in 2017, the implementation of a beverage excise tax on sugar-sweetened and artificially sweetened beverages was associated with significantly higher beverage prices and a significant and substantial decline in volume of taxed beverages sold. This decrease in taxed beverage sales volume was partially offset by increases in volume of sales in bordering areas.
Roberto et al. (Tue,) studied this question.