This week, the governor of Connecticut proposed a statewide tax on sugar-sweetened drinks. Several cities have already enacted such soda taxes to raise money and fight obesity(肥胖).And here's new evidence suggesting that these taxes do work—although sometimes not as well as hoped. Kris Madsen, an associate professor of public health at the University of California, Berkeley, has been studying soda taxes, in part because she's convinced sugary drinks are a threat to society and a direct cause of obesity. "It's a pretty high bar for public health to be able to say that something is causing a major epidemic," she says."We can do that for sugar-sweetened beverages." Berkeley was the first U.S. city to tax those drinks, making them more expensive, and Madsen is leading a team of researchers that are trying to see how the tax is working. "We've been going out to the same neighborhoods every year for the last five years, and we've been asking people the same questions," she says. Researchers interview people on the street, primarily in low-income neighborhoods. They started doing this before the soda taxes came into effect four years ago, and they've continued every year since."We saw a 52 percent decline in consumption over the first three years since the tax came into effect," she says."This has a huge impact." Madsen's study was published online this week by the American Journal of Public Health. Mexico, in fact, put in place a tax on sugar-sweetened beverages in 2014. That tax is smaller than the soda taxes in the U.S.,and its effect on consumption has also been smaller. According to one study, consumption of sugary drinks fell on average by about 8 percent as a result of the tax.