Small sales taxes on soft drinks are insufficient to reduce consumption of soda or curb obesity among children, according to a new a new study in Health Affairs.

Such small taxes may reduce consumption in some subgroups, such as children at greater risk for obesity. But to reduce overall soda consumption, the taxes would have to be downright draconian, structured as excise taxes that would increase the shelf price of the product rather than sales taxes collected at the cash register.

An 18 percent soda tax proposed and then dropped from New York's Executive Budget last year, for example, could help prevent excessive weight gain between third and fifth grades by 20 percent, the authors say.

"If the goal is to noticeably reduce soda consumption among children, then it would have to be a very substantial tax" said Roland Sturm, the study's lead author and a senior economist at the RAND Corporation. "A small sales tax on soda does not appear to lead to a noticeable drop in consumption, led alone reduction in obesity."

Researchers estimated the potential effect of soft drink taxes on children's consumption and weight by examining differences in existing sales taxes on soft drinks between states. Details about state soda taxes were compared to information about weight and soda consumption among 7,300 children enrolled in the Early Childhood Longitudinal Study, which has been gathering information about a national group of children for many years.

Children studied reported drinking an average of six sodas per week, but there was wide variation among the group. Fifteen percent reported drinking no sodas in the prior week, while 10 percent consumed two or more sodas per day. The amount of soda purchased at school was small.

The analysis could find no significant link between the consumption of soda or weight gain among children and differential taxes on sodas versus other foods. Existing differential taxes (taxes that are imposed on sodas and not other food items sold in grocery stores) are small, averaging 3.5 percent and none are larger than 7 percent.

The higher sales tax on soda in some states did seem to reduce soda consumption and curb weight gain among children at higher risk for obesity -- those who were heavier, children from low-income families, African-American children and those who watched a lot of television. Children in all these groups drank more soft drinks than children in general.

The impact was more pronounced for children from these groups who had access to soft drinks at school. Price effects may be stronger in school settings where cafeterias or vending machines round prices up, although there are alternative explanations, according to the study.

The fact that small sales taxes have no strong effect on consumption should not be surprising and the much larger soda taxes recently proposed in several areas are likely to have a much larger effect.




Citation: Sturm et al., 'Soda Taxes, Soft Drink Consumption, And Children’s Body Mass Index', Health Affairs, April 2010; doi: 10.1377/hlthaff.2009.0061