Evaluation of the City of Seattle’s Sweetened Beverage Tax

In June 2017, the City of Seattle passed an Ordinance to impose a 1.75-cent-per-ounce tax on sugary beverages. The ordinance that created the Sweetened Beverage Tax also required the City to work with academic researchers to assess the impact of the tax (Ordinance 125324, Section 5B). We have proposed to evaluate the impact of this tax on economic outcomes, health behaviors and intermediate health outcomes. The evaluation shall also assess, but not be limited to, the process of implementing the tax. Finally, the Ordinance requires identification and assessment of food deserts in the city, and an evaluation of the effectiveness and efficiency of the foodbank network in the city. 

This five-year evaluation is a collaboration between Public Health – Seattle & King County, the University of Washington, Children’s Research Institute, and Fred Hutchinson Cancer Research Center.

Our evaluation plan consists of the following main components.

• We will assess how prices of taxed and untaxed beverages change in response to the tax by collecting beverage prices before and after the tax in Seattle as well as in a comparison area.
• We will assess whether children’s dietary intake of sugary drinks changes in response to the tax by enrolling a cohort of children in Seattle and the comparison area, assessing baseline intake and then following them over time to see how sugar beverage intake changes. We will focus on children and parents with lower income because populations with limited resources may be more sensitive to these taxes than populations with higher income. We will also conduct follow-up interviews with parents to understand their experiences with the tax and reasons for changing their beverage intake and the beverages they serve to their children over time.
• We will interview key stakeholders to evaluate their perceptions and experience with the tax.
• We will conduct an analysis of the impact of the tax on jobs and revenue using administrative data from the state of Washington.
• We will evaluate the impact of the tax on children’s body mass index, using data from WIC records and from the Healthy Youth Survey. We will administer a survey using a random digit dialing to get a representative sample of Seattle and to test how norms and attitudes about the tax and sweetened beverages change in association with the tax. 

The study team has published work so far from 1) the retail audit, a survey of grocery, quick-service restaurants, and beverage shops, to understand beverage prices before and after the tax, 2) the cohort of children and parents, a study to understand changes in sugary beverage intake in response to the tax, 3) the economic equity of sugary beverage taxes, 4) the norms and attitudes survey, a survey of city residents assessing whether the tax changes residents’ perceptions about sugary beverages and the tax itself, and 5) the assessment of the healthy food availability, areas in the City with limited healthy food availability, and the City’s food bank network.

Resources

• All published reports are available for download on the City of Seattle Sweetened Beverage Tax Community Advisory Board webpage
• Supplemental Materials: Availability and Price of Healthy Food in Seattle by Neighborhood Sociodemographic Characteristics