Seattleites: Your next soda could be taxed. Here's how it's worked so far in California...

SEATTLE -- Backers behind a soda tax proposed in Seattle right now could look to a study out of Berkeley, California.

The study out Tuesday shows the sales of sugary drinks in Berkeley went down nearly 10% in the year after the tax was imposed in the city. At the same time, sales of water and other untaxed drinks increased.

The study relied on checkout data from 15.5 million supermarket transactions.

Seattle's mayor is proposing a two-cents per ounce tax on sodas, energy drinks, sports drinks, sweetened teas and more.

We asked one of the authors of the study if she thinks Seattle's proposal would be effective.

"Our study to date would suggest this is a good public policy and if the money is used wisely, which is up to Seattle voters to decide how to use it, it may be able to help your city become healthier," said Dr. Lynn Silver.


But not everyone is for it. The owner of Burger Boss in Seattle used his sign to advertise against the tax, when he learned it would double the cost of his fountain drinks.

There have also been questions about if taxing surgary drinks is effective. 

Mayor Ed Murray estimated that the tax would generate 16 million dollars a year for education funding and to help improve graduation rates of minority youth.

The FDA recommends that no more than ten-percent of your daily calories come from added sugars. That is 50 grams, or about 12.5 teaspoons of sugar if you're on a 2,000 calorie diet.

WATCH: A 20 ounce bottle of coke exceeds that daily recommendation, with 65 grams of sugar, or the equivalent of 15 teaspoons of sugar. 

This coke = the amount of sugar in that cup, exceeding daily recommendations for sugar intake. 

Seattle's sugary tax proposal is expected to be brought to the Seattle City Council soon.