005 - Impact of soda tax on soda consumption and obesity prevalence in Californian cities

Objective
In 2014, Berkeley, California, became the first US jurisdiction to pass a sugar sweetened beverage (SSB) excise tax (1 cent per ounce). Three other localities in California (Albany, Oakland, San Francisco) followed suit and approved similar 1-cent-per-ounce taxes in 2016. We aim to conduct the first large-scale intermediate evaluation of SSB excise tax in these cities. This is also the first time to include obesity as health outcome.
Research Design and Methods
We used California Health Interview Survey (CHIS) adult data from 2009 to 2021. We obtained SSB excise tax information from city council websites. We assumed that once the SSB excise tax policy was implemented it remained so unless explicitly repealed at some point. The policy was implemented in 2015 in Berkeley, 2018 in San Francisco, 2017 in Oakland and Albany. We estimated the number of times drinking soda per week as well as obesity prevalence. Data for soda consumption is available until 2018. A BMI ≥30 kg/m2 is obese for adults 20 years and older. Propensity score matched difference-in-difference (DID) was implemented. We selected controls from non-SSB tax cities. Controls were matched on age, gender, race/ethnicity, marital status, smoke, education, employment, poverty, general health conditions, diabetes, and high blood pressure.
Results
Soda tax decreased the number of times an individual consumes soda per week in Berkeley (ATT, average treatment effect among treated=-0.61, 95%CI -0.69, -0.54). Soda tax decreased obesity prevalence in Berkeley, Oakland and San Francisco (ATT=7%, 95%CI -8%, -6%; ATT=4%, 95%CI -5%, -3%; ATT=8%, 95%CI -9%, -7%. There was no change in Albany (ATT=0, 95%CI -2%, 1%).
Conclusion
SSB excise tax decreased soda consumption and obesity prevalence in most cities. It can be an effective policy response to reduce SSB consumption and build healthier beverage environments.
Abstract word count: 290

soda tax, obesity, California, difference in difference 

Beginner

Knowledge

International Conference on Health Policy Statistics 2023