Evaluation Reports
The ordinance that created the Seattle Sweetened Beverage Tax (Ordinance 125324) also required the City to work with academic researchers to evalute the tax's effect on health and economic outcomes.
The Seattle Office of the City Auditor contracted with Public Health - Seattle & King County to lead the evaluations. Public Health contracted with the University of Washington and Seattle Children's Research Institute to conduct certain parts of the evaluation. The Sweetened Beverage Tax Community Advisory Board also provided input on certain parts of the evaluation.
From 2017-2023, the evaluation team collaborated on many studies designed to assess the impacts of the SBT on the prices of sugary drinks, store revenues, health outcomes, and health behaviors and beliefs. In this time, the SBT evaluation team produced 13 reports and five peer-reviewed publications.
Click here for a summary of the key evaluation findings, five years after tax implementation. Below you can access full reports.
Sweetened Beverage Tax (SBT) Evaluation Reports
Sweetened Beverage Tax Two Year Report: Store Audits
Published May 2023
The primary objective of the store audits was to see what portion of the 1.75 cents per ounce tax on sweetened beverages levied on beverage distributors was passed through to customers (“price pass-through”) in Seattle. In this report, the researchers examine price pass-through of the tax approximately two years after the tax was implemented.
Sweetened Beverage Tax 24 Month Report: Child Cohort Examining Beverage Consumption
Published May 2023
The primary objective of this report was to explore whether consumption of sugary beverages that were subject to the Sweetened Beverage Tax in Seattle changed from before to 24 months after the tax, among children and parents living in Seattle, compared to children and parents living in the Comparison area where the same beverages were not subject to the Sweetened Beverage Tax. We also explored whether there were different child and parental changes in consumption of non-taxed beverages (including water) by location, and parents’ awareness, attitudes, and experiences with the Sweetened Beverage Tax.
Published May 2023
This was an interim report of baseline characteristics for the adults and youth included in the datasets used to study the impact of the Sweetened Beverage Tax on adult and youth weight outcomes, as measured by body mass index (BMI).
Published May 2023
This study used a quasi-experimental design to evaluate the association between Seattle’s Sweetened Beverage Tax and changes in body mass index (BMI) - a measure of obesity, among a patient population of adults in Seattle and surrounding areas.
Published May 2023
This study used a quasi-experimental design to evaluate the association between Seattle’s Sweetened Beverage Tax and changes in body mass index (BMI), a measure of obesity, among a patient population of children and youth in Seattle and surrounding areas.
Published May 2023
The objectives of this study were to understand why parents in the SeaSAW cohort decreased or did not decrease their sugar-sweetened beverage consumption after implementation of the Sweetened Beverage Tax and explore whether reasons differed for parents in Seattle versus those in the comparison area.
Published May 2023
This report examined the association between the Seattle Sweetened Beverage Tax and changes in sugar-sweetened beverage consumption and weight status among adolescent students.
Sweetened Beverage Tax 24 Month Report: Revenues
Published January 2023
The goal of this portion of the SBT Evaluation was to assess the degree to which Seattle's Sweetened Beverage Tax may have affected the business viability of small food stores or convenience stores in Seattle.
Published August 2021
The SBT Evaluation team undertook this norms and attitudes study to understand what Seattle-area adults believe about Seattle's Sweetened Beverage Tax and sugary beverages, and how those thoughts may have changed over the course of two years. This new report provides follow-up data on what the research team learned about norms and attitudes found in its 2018 baseline report, which was done before implementation of the Sweetened Beverage Tax.
12-Month Report: Store Audits & Child Cohort
Published April 2020
This report summarizes findings from data collected 12 months after implementation of the Seattle Sweetened Beverage Tax on the price of beverages in stores and the beverage consumption of a cohort of lower-income children and parents living in Seattle and the South King County area.
Healthy Food Availability & Food Bank Network Report | Slides | Summary Report | Summary Report in Somali
Published February 2019
This report begins with a literature review of the different ways to define and measure food access. Section 2 identifies Healthy Food Priority Areas in Seattle based on areas of the city with higher poverty rates, longer travel times to healthy food retailers, and greater density of unhealthy food retailers. Section 3 reports on the price and availability of healthy food in Seattle stores. Section 4 describes who experiences food insecurity in Seattle and who falls in the "food security gap". Finally, Section 5 assesses the food bank network in Seattle.
Six-month Store Beverage Prices Report | Slides | FAQs | Summary Report | Summary Report in Somali
Published January 2019
Seattle's Sweetened Beverage Tax is a tax on the distributors of sugary beverages. However, a key evaluation question is whether the tax is passed on to consumers via higher retail prices. This report presents findings on beverage prices six months after the tax began compared to the baseline (pre-tax) prices.
Baseline Report: Evaluation of Seattle's Sweetened Beverage Tax | Slides
Published August 2018
This report describes findings from the baseline (pre-tax) evaluation studies that required data collection in both Seattle and the comparison areas before the tax went into effect in January 2018. The study components include 1) store surveys to collect baseline beverage price data, 2) surveys of beverage consumption among a cohort of children and parents, 3) surveys of norms and attitudes about a sugary beverage tax, and 4) interviews and focus groups about perceptions of the sugar-sweetened beverages and implementation of the tax.
Other Research and Publications on Seattle's Sweetened Beverage Tax
Jones-Smith JC, Knox MA, Chakrabarti S. Sweetened Beverage Tax Implementation and Change in Body Mass Index Among Children in Seattle. JAMA Netw. Open. 2024;7(5):e2413644.
Powell, L. Evidence of the Impacts of the Seattle Sweetened Beverage Tax. Presentation to the University of Washington and City of Seattle. September 22, 2022.
Jones-Smith JC, Knox MA, Coe NB, et al. Sweetened beverage taxes: Economic benefits and costs according to household income. Food Policy. 2022 July, Volume 110.
Powell, LM, Leider J. An Overview of the Impact of the Seattle, Washington, Sweetened Beverage Tax on Prices, Demand, Substitution, and Sugar Sold. Research Brief No. 124.
Powell LM, Leider J. Impact of a sugar-sweetened beverage tax two-year post-tax implementation in Seattle, Washington, United States. J Public Health Policy. 2021 Dec;42(4):574-588.
Powell LM, Leider J. The impact of Seattle's Sweetened Beverage Tax on beverage prices and volume sold. Econ Hum Biol. 2020 May;37:100856.
Oddo VM, Krieger J, Knox MA, et al. Perceptions of the possible health and economic impacts of Seattle's sugary beverage tax. BMC Public Health. 2019;19(1):910.
Powell LM et al. Intake of Sugar-sweetened Beverages among Adults in Seattle, WA, 2017. Research Brief No. 106. Illinois Prevention Research Center, University of Illinois at Chicago. Chicago, IL. November 2018.