After years of inconclusive data, new evidence suggests that Seattle’s soda tax is working—and it’s working really well

Ever feel like it’s impossible to make sense of whether soda taxes actually work to reduce sugar consumption? We don’t blame you. For years, proposals to levy fees on sugary drinks have stoked impassioned debate, and generated thousands of pages of competing research over their effectiveness. Just as quickly as some jurisdictions have implemented such policies, others have responded by banning them, creating a confusing patchwork of soda legislation across the country.

For readers who aren’t in the weeds of public health, the topline findings of soda tax studies may even seem contradictory. Just take this sample of headlines, for example, all published in the past few years: “Soda taxes really do work,” reads one article in TIME. “Philly’s soda tax didn’t lead to people drinking less soda, study says’,” reads another from The Philadelphia Inquirer. And then there’s this post from NPR: “U.S. Soda Taxes Work, Studies Suggest—But Maybe Not As Well As Hoped.”

It’s enough to make you throw your hands up and think about simpler things instead. But stick with us as we parse out a new, first-of-its-kind study—one that may tell us once and for all just how much soda taxes cut back sugar consumption in a major city that adopted them. Spoiler: The reductions are big.

In a recent analysis, researchers used a large set of grocery shopping data to track food and drink sales before and after the city of Seattle implemented a sugary drinks tax in January of 2018. The data set itself—gathered by marketing insight firm Nielsen—was huge, representing 45 percent of all food store sales in the city for 2017, 2018, and 2019. To create a control group, researchers also obtained the same data for the nearby city of Portland, Oregon, which doesn’t have a sugary drinks tax in place.

To account for different sugar levels in various beverages, a team led by Lisa Powell, health policy professor at the University of Illinois at Chicago, coded each type of drink by its exact sugar content. In doing so, they found that the total amount of sugar sold through taxed drinks dropped by 23 percent in Seattle compared to sales of the same products in Portland, one year after the implementation of the soda tax. That decline held for the following year as well, suggesting that the dip was not just a fluke.