While most media coverage after the election focused on Donald Trump’s surprising victory, four cities quietly voted to pass soda taxes. Voters in San Francisco, Oakland, and Albany, California passed a one-penny-per-ounce tax on sugary soft drinks. In Boulder, Colorado, it’s two cents per ounce. (The Cook County Board of Commissioners, which oversees Chicago and the surrounding suburbs, approved a similar tax last week.)

Soda is packed with sugar—a can of Coke, for example, has 39 grams of the sweet stuff. For years, scientists have blamed soft drinks as one of the main culprits behind America’s obesity epidemic. They’re the epitome of empty calories.

The thinking is: If we add a tax to soda (in the same we do to a pack of cigarettes), prices will go up and people will drink less. It’s worked before. In low-income neighborhoods in Berkeley, California, soda drinking dropped by one-fifth after the city passed a tax on sugary soft drinks.

But economists caution that this is just the first step. When you look at the example of cigarettes, excise taxes (which made a pack more than $10 in some states) had a small impact on smoking rates, Roland Sturm, a senior economist and professor of policy analytics at RAND, told Vox. The bigger shifts happened when smoking became less socially acceptable.