Adherence
Implementation of a sugar-sweetened beverage (SSB) excise tax leads to a significant decline in the volume of SSB sales, accompanied by a substitution effect toward untaxed beverages (particularly water), without increasing overall consumer spending per transaction.
A tax on sugary drinks successfully reduces the amount of sugary drinks sold by making them relatively more expensive. Consumers respond by buying less sugary drinks and more water or other untaxed beverages, keeping their total grocery bill roughly the same. This policy lever works through economic substitution rather than direct health mandates.
SSB sales in Berkeley fell significantly in two chains of large supermarkets, while sales of untaxed beverages, especially water, and of all beverages increased. From the available data, there was no evidence of higher consumer spending, nor was there a greater reduction in store revenue per transaction in relation to comparison sites.
Why this rating
Strong observational design with large scanner datasets (15.5 million checkouts) and control groups, though limited by lack of direct health outcome measures and self-reported consumption data.
Source
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
Lynn Silver et al. · PLoS Medicine · 2017
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