A new study of how taxes might be used to curb consumption of sugary drinks suggests that applying a tax based on the amount of calories contained in a serving rather than its size would be more effective.
The study, financed by the Robert Wood Johnson Foundation, which has long advocated taxing sodas and other sugary drinks as part of its efforts to reduce childhood obesity, found that consumption of calories in drinks would drop 9.3 percent if a tax of four-hundredths of a penny for every calorie was added to the price, but fall by just 8.6 percent under a tax of half a cent for each ounce in a can or bottle.
A calorie-based taxing system would also be fairer to consumers, said Chen Zhen, a research economist at the food and nutrition policy research program at Research Triangle Institute and the lead author of the study.
"It provides a better incentive to the consumer to switch to lower-calorie drinks, which would be taxed at a lower rate than higher-calorie drinks," Dr. Zhen said. "One of the concerns about taxing ounces of sugar-sweetened beverages is that consumers are paying the same tax whether they buy 12 ounces of a drink with 150 calories or 12 ounces of a drink with 50 calories."
At a tax rate of four-hundredths of a penny per calorie, six cents would be added to a 12-ounce can of Coca-Cola, for example, Dr. Zhen said, while only four cents would be added to a 16-ounce bottle of Vitaminwater.
"From a public health point of view, it makes a lot of sense to tax the sugar, which is the most harmful part of these drinks," said Harold Goldstein, executive director of the California Center for Public Health. "We want to shift consumers from drinking more sugar to drinking less, so taxing beverages with more sugar more makes sense."
The California Senate last week passed a bill for warning labels on sugary soft drinks. The State Assembly has not yet voted on the bill.
Sales of sugary drinks already are falling, and Christopher Gindlesperger, a spokesman for the American Beverage Association, the trade group that represents the soda companies, noted that a variety of soda tax proposals have been defeated in various states over the last several years. Just last week, the Illinois House voted down a bill that would have taxed sugary soda at a rate of one cent an ounce, specifically citing the cost to consumers.
Arkansas and West Virginia tax soda — and are among the top 10 states for obesity. "Over the course of last several years, taxes on soft drinks and other sugar-sweetened beverages have gone nowhere, and it's in large part because people don't want it," Mr. Gindlesperger said.
He also noted that one of the authors of the study, Ryan R. Ruff, was director of research and evaluation at the New York City Department of Health and Mental Hygiene in the Bloomberg administration, which waged a war on sugary drinks.
Dr. Zhen previously has done research finding that taxes on sugary drinks might not be as effective as a high tax on cigarettes in reducing consumption because consumers can substitute a high-calorie food that is not taxed for a high-calorie soda that is.
"We are not saying you should tax sugar-sweetened beverages," Dr. Zhen said, speaking about the new study. "We're saying that if you're going to tax them, the best way of doing that is on the basis of calories. We are trying to stay away from the politics."
The study was published online by the American Journal of Agricultural Economics.
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