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

INTRODUCTION: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.