Pass-through of the Oakland, California, sugar-sweetened beverage tax in food stores two years post-implementation: A difference-in-differences study.

Abstract

Taxes on sugar-sweetened beverages (SSBs) have gained support as a policy response to adverse health effects associated with SSB consumption. On July 1, 2017, Oakland, California, implemented a one-cent/ounce tax on SSBs with ≥25 calories/12 fluid ounces. This study estimated the long-term impact of the tax on taxed and untaxed beverage prices. Data on 5,830 taxed and 5,146 untaxed beverage prices were obtained from 99 stores in Oakland and 111 stores in Sacramento (comparison site), California, in late May-June 2017 and June 2019. Linear regression difference-in-differences models were computed with store and product fixed effects, with robust standard errors clustered on store, weighted based on volume sold by beverage sweetener status, type, and size. Taxed beverage prices increased by 0.73 cents/ounce (95% CI = 0.47,1.00) on average in supermarkets and grocery stores in Oakland relative to Sacramento and 0.74 cents/ounce (95% CI = 0.39,1.09) in pharmacies, but did not change in convenience stores (-0.09 cents/ounce, 95% CI = -0.56,0.39). Untaxed beverage prices overall increased by 0.40 cents/ounce (95% CI = 0.05,0.75) in pharmacies but did not change in other store types. Prices of taxed individual-size soda specifically increased in all store types, by 0.91-2.39 cents/ounce (p<0.05), as did prices of untaxed individual-size soda in convenience stores (0.79 cents/ounce, 95% CI = 0.01,1.56) and pharmacies (1.66 cents/ounce, 95% CI = 0.09,3.23). Two years following SSB tax implementation, there was partial tax pass-through with differences by store type and by beverage type and size within store type.