According to a new study, consumption of sugary drinks — at least in some neighborhoods — is down by a whopping 20 percent.
That estimate results from what Kristine Madsen, a researcher at the University of California, Berkeley’s School of Public Health, calls a “perfect natural experiment.” In the fall of 2014, voters in Berkeley and San Francisco, on opposite sides of the San Francisco Bay, voted on proposals to tax sugar-sweetened drinks at the rate of one cent per fluid ounce.
The proposals were aimed at reducing consumption of these drinks, which are blamed for increasing rates of obesity and Type 2 diabetes.
Before the votes, Madsen and a small army of collaborators began laying the groundwork for efforts to measure whether such a tax would actually work.
They targeted low-income neighborhoods of each city, as well as Oakland, and carried out surveys of people they met on the street. “We asked how often they drank various beverages,” Madsen says.
They recorded the answer and waited for the vote.
The tax did not pass in San Francisco. But it did in Berkeley. So sugary drinks became more expensive Berkeley, but not in San Francisco.
Madsen and her collaborators then returned to the same neighborhoods, with the same questions. “I would say, ‘How often do you drink regular soda, like a Coke, or Sprite? Once a week? Once a month?’ And some people would just say, ‘Well, I drink it every day.’ And what we were trying to do was get some way of making everybody equal, so that everybody could be expressed as times per day that they drank soda.”
Before the vote, the answers had been very similar in both cities. The average person drank about 1.25 sugary beverages per day.
After the vote, those responses diverged. In San Francisco, where there was no tax, …