Seattle's Sweetened Beverage Tax linked to improved public health outcomes

An evaluation with KPWHRI researchers looked at the impacts of the tax so far

A new study suggests that Seattle's Sweetened Beverage Tax (SBT) has had numerous positive impacts since going into effect in 2018.

A team of researchers from Public Health — Seattle & King County, the University of Washington, and Seattle Children’s Hospital Research Institute recently completed a multi-faceted evaluation of the tax’s effect on public health outcomes and its economic impact. Kaiser Permanente Washington Health Research Institute (KPWHRI) Senior Investigator David Arterburn, MD, MPH, collaborated on the study, and Jane Anau, BS, and Joey Eavey, MSPH, helped to collect and prepare the data from Kaiser Permanente Washington.

“The goal of this type of beverage tax is to act as a deterrent against buying and consuming sugary drinks,” said Jessica Jones-Smith, PhD, MPH, RD, co-investigator and associate professor of Health Systems and Population Health and Epidemiology with the University of Washington School of Public Health. “One of the most important findings of our study is that we see impacts on health outcomes among both youth and adults in association with the tax.”

Health outcomes 

Sugar-sweetened beverages are a known contributor to several health issues, including lower diet quality, weight gain, and diabetes. Public health agencies have long tried to steer consumers toward healthier options, with varying impacts. Seattle’s SBT has shown positive results.  

“The improved BMI [body mass index] data (provided by Kaiser Permanente Washington and Seattle Children's Hospital), while a modest improvement, is important because very few population-level interventions have shown any impact on BMI,” said Jones-Smith. “We expect the impacts to be small for this type of intervention. Nevertheless, studies have shown that small changes in BMI at a population level are expected to result in reductions in chronic conditions such as diabetes. In youth, we found small decreases in BMI and in adults we found lower gains in BMI as compared to adults in a nearby comparison area.”   

“This study highlights the significant role that large health systems, such as Kaiser Permanente, can play in assessing the effects of policy interventions at the community level,” Arterburn said. “Because the study used anonymized electronic health record data, it was able to be conducted at a significantly reduced cost and with much faster results compared to a traditional observational study or randomized trial.”

Health behaviors and beliefs 

The researchers also conducted a longitudinal cohort study, a survey of norms and attitudes, and in-depth qualitative analyses to understand and measure health behaviors, beverage consumption, and dietary patterns over time and as a result of the SBT tax.  

The study found that families reported drinking fewer sugary drinks subject to the tax. However, the decrease was similar for families in Seattle and families living in the comparison area who were not subject to the tax. “We conducted qualitative interviews to understand why families in the area without the tax also decreased their beverage intake,” said Jones-Smith.  

“These interviews suggested that some families in the comparison area were exposed to media coverage about the tax and this raised their awareness of the unhealthfulness of sugary beverages, while others bought fewer drinks due to price increases when shopping in Seattle,” said Leah Neff Warner, MPH, a doctoral candidate in epidemiology at the University of Washington School of Public Health who helped lead the qualitative study.    

While the study could not directly attribute the decline in consumption of taxed beverages to the tax, other research found a substantial decline in purchases of taxed beverages in Seattle relative to the comparison city. Qualitative interviews revealed that reasons for decreasing beverage consumption were similar among participants in Seattle and the comparison group, including health concerns, beverage prices, media coverage, and participation in the study, with beverage prices being a stronger theme among those in Seattle.  

Economic impact 

While initial debate surrounding the SBT focused heavily on the economic impact to businesses such as independent markets and convenience stores, which derive a large percentage of revenue from the sale of snacks and refreshments, the data indicated no such negative impact. The study found that the tax was essentially passed through to customers without any residual effect on snack or food prices or small business closures or revenue. 

“We studied whether these small stores experienced a loss of revenue or an increased likelihood of going out of business in association with the tax,” said Jones-Smith. “We compared stores in Seattle to well-matched stores in nearby cities and found the tax had no detectable impact on store total revenue or on likelihood of store closure.” In fact, by the second year after the tax, there was an increase in revenue for Seattle stores compared to other stores. “The data suggests that customers did not stop purchasing items at these businesses, so that, on net, revenue did not decrease.” 

Positive impacts now and in the future 

“Taken together, the tax seems to be having the positive intended consequences of beneficial impacts on BMI, which is important for future risk of chronic conditions such as diabetes,” said Jones-Smith. “It also suggests minimal negative unintended consequences for business revenue and likelihood of closure. In addition, the funds from the tax are used for important public health programs aimed at improving health equity.”   

Revenues generated by the tax are used to fund healthy food access programs and equitable access to child health and early learning programs as well as community-led health promotion campaigns.

The other core co-investigators/coauthors on the reports were:

• Melissa Knox, PhD, Department of Economics, University of Washington
• Jessica Godwin, PhD, Center for the Studies of Demography and Ecology, University of Washington
• Lina Pinero Walkinshaw, MPH, Department of Health Systems and Population Health, University of Washington
• Stephen Mooney, PhD, MS, Department of Epidemiology, University of Washington
• Nadine Chan, PhD, MPH, and Lin Song, PhD, Public Health — Seattle & King County
• Brian Saelens, PhD, Seattle Children’s and University of Washington

This study was part of a collaborative effort examining all aspects of the SBT. The summary report can be found on the Seattle City Auditor's website.

This has been adapted from a news story by the University of Washington School of Public Health.