Changes in prices, sales, consumer spending, and beverage consumption one year after a tax on sugar-sweetened beverages in Berkeley, California, US: A before-and-after study
Fig 4
Point-of-sale adjusted mean daily volume of beverages sold (ounces per transaction) in Berkeley versus non-Berkeley stores.
(A) Point-of-sale taxed beverage volume sold (ounces per transaction).(B) Point-of-sale untaxed beverage volume sold (ounces per transaction).(C) Point-of-sale taxed and untaxed beverage volume sold (ounces per transaction).(D) Percent change in post-tax untaxed beverage sales (ounces per transaction) in relation to counterfactual in Berkeley and non-Berkeley stores. Models account for store ID, month, year, day of week, holiday and holiday eve, number of transactions (linear and quadratic), a post-tax indicator, and interactions of store ID with the post-tax indicator, month, and year variables, correcting the standard errors by clustering the analyses at the city level. Back-transformation uses Duan smearing. Model n = 10,152. Vertical lines demarcate the pre-tax period (January 2013–December 2014), the ambiguous period (January–February 2015), and the post-tax period (March 2015–February 2016). To derive the counterfactuals, we predicted the volume of taxed and untaxed beverages sold if the post-tax indicator = 0 for March 2015–February 2016. Full results can be found in S10 and S11 Tables. *Statistically significant difference between the counterfactual and observed volumes sold during the entire post-tax period at p < 0.05. **Statistically significant difference between the counterfactual and observed volumes sold during the entire post-tax period at p < 0.01. Source: point-of-sale data from two chains of large supermarkets in the Bay Area obtained by the Public Health Institute.