In an effort to curb obesity, many states have levied taxes on soft drinks. But a recent report co-written by a Yale professor suggests that these taxes do not significantly affect obesity levels.
The study, which was published online on Oct. 15 by Contemporary Economic Policy, found that a 1 percent tax increase on sodas resulted in a body mass index decrease of 0.003 points — equivalent to less than a tenth of a pound for a man of average height — suggesting small taxes on soft drinks have a minimal effect on people’s consumption.
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Body mass index (BMI) is a weight-to-height ratio used to measure obesity. A BMI over 25 suggests that a person is overweight, while a BMI over 30 indicates obesity.
The study analyzed data provided by the Center for Disease Control over a 16-year period, with a sample size of about 2.5 million people.
Researcher Jason Fletcher, an assistant professor of epidemiology and public health, said the average current tax on soft drinks is 3 percent, which he considered too small to make a difference.
“Most people don’t even think there is a soda tax,” Fletcher said. “At the current rate, [the soda taxes] don’t reduce obesity very much. But it’s still a point of interest for policy makers to think about a big tax, which might be more visible to the consumers. [Then] they might actually know they are being taxed. They might actually change their behavior.”
Fletcher said while a bigger tax might be effective at curbing obesity, he is not certain because of a lack of data. According to Fletcher, the largest soda tax ever implemented in the U.S. was a 10 percent tax in Ohio 14 years ago, which has since been abolished.
Researcher David Frisvold, a professor at Vanderbilt University, said soda taxes are nothing new, having been around before the 1920s. With the public debate about “obesity tax” increases in recent years, the study sought to clarify the effects of these taxes, Frisvold said.
Frisvold suggested other alternatives to curb obesity, such as improving nutritional education and exercise opportunities.
“I think, generally speaking, you’re going to find policies that target younger children are going to have more of an effect, simply because nutritional patterns are not quite as established for young children than adults,” he said.
While the study showed that soft drink taxes have a greater impact on lowering BMI for lower-income, female, middle-aged and older individuals, Fletcher said the results were not significant enough to warrant attention.
“All of the effects are so, so small, in some ways they don’t even matter,” Fletcher said. “It’s going from 1/100 of a pound to 1/150 of a pound. We don’t have the evidence to parcel out the gender effect or the income effect. So, small taxes don’t seem to work for any group.”
Yale researcher Kelly Brownell, who co-wrote a report last month advocating a penny-per-ounce excise tax on soda and other sugar-sweetened beverages, agreed that the existing taxes on soft drinks are too small to decrease consumption.
“The results of the study are not surprising and speak to the need for a larger tax, like the penny-per-ounce tax on sugared beverages we proposed,” said Brownell, the head of the University’s Rudd Center for Food Policy and Obesity, in an e-mail.
The third researcher of the study, Nathan Tefft, an assistant professor of economics at Bates College, said he and his colleagues are currently working on a follow-up study that focuses on the relationship between soft drink taxes and the prevalence of obesity in children and adolescents.
According to the Kaiser Family Foundation, a nonprofit organization that analyzes health issues, Connecticut has no sales tax on general food items but a 6 percent tax on soft drinks. Rhode Island, which has a 7 percent tax on soft drinks, has the highest soda tax of any state.
Correction: October 21, 2009
The original headline of of this article, “Soda tax doesn’t loosen belts,” was inaccurate. In fact, the study presented in the article found that soda taxes did not tighten belts, that is, they were not effective in causing people to drink less soda and lose weight.