BERKELEY, Calif. – Apparently, taxing sugary soft drinks can make people less likely to drink them. At least that’s what researchers found when analyzing residents of low-income areas in Berkeley, Oakland and San Francisco, Calif., four months after Berkeley’s soda tax went into effect, the New York Times reports.

Published this week in The American Journal of Public Health, self-reported drinking of sugared soda dropped by 21% in Berkeley’s low-income communities, but jumped 4% in Oakland and San Francisco. Berkeley residents also said they were consuming more water.

This study seems to support research from Mexico—its national soda tax went into effect in 2014—showing sales of sugared beverages decreased by around 17% in poor neighborhoods. But overall, in May, a report found that soft drink sales have surged in Mexico.

“At least in one city, we have found evidence that a sugar-sweetened beverage tax reduced consumption in disadvantaged communities,” said Jennifer Falbe with the University of California at Berkeley’s School of Public Health and one of the paper’s authors.

However, the soda industry noted that the survey had problems with its methodology. “The authors of this street survey acknowledge that it had a number of flaws, and there is no indication that the tax had or will have a measurable impact on public health,” said William Dermody, vice president for policy at the American Beverage Association.

Philadelphia recently approved a soda tax. Meanwhile, other countries are considering their own soda tax, including Australia and the United Kingdom.