The Tax Collector

Still Looking for the Health Effect of SSB Taxes

A new study in Health Economics reminds us we’re still looking for evidence for the health effect of sugar-sweetened beverage (SSB) taxes. It hasn’t shown up yet. But we’re still waiting hopefully. This latest study comes from John Cawley, Michael Daly, and Rebecca Thornton. They estimated the effect of an SSB Tax in Mauritius on consumption and BMI in adolescents in youth. Unfortunately, they didn’t find much:

“Results of difference-in-differences models indicate that the tax in Mauritius had no detectable impact on the consumption of SSBs or the BMI of the pooled sample of boys and girls. However, models estimated separately by sex indicate that the probability that boys consumed SSBs fell by 9.4 percentage points (11%).”

Effects on SSB Consumption and BMI

Like most other tax effect analyses, this is observational research. Cawley et al analyzed self reported SSB consumption and BMI for youth aged 12 to 17. Mauritius implemented an SSB tax on their island in 2013. So the researcher analyzed data from 2011 and 2017. For a comparison country the researchers selected Maldives, another island nation. This worked for them because Maldives had many similarities to Mauritius, and it had availability of comparable data for analysis.

Cawley used a difference-in-differences model to estimate the SSB tax effect on both BMI and consumption. They found no effect on either measure in the pooled sample of girls and boys. But when they separated out the boys, they could find an 11 percent reduction in consumption. Even so, they could not tease out an effect in either girls or boys on BMI.

Cold, Hard Economic Analysis

The matter of fact conclusions of economists stand in stark contrast to the enthusiasm we find from many public health scholars. Recently in JAMA Pediatrics, Tadeja Gračner and colleagues also found a no effect on BMI in the population of Mexican youth they studied. But they teased out a small effect in the girls they studied in some of the geography, for some of the heavier girls.

Even though that research found no overall effect, Jennifer Falbe and colleagues celebrated these results as a win for the cause of taxing soda. “It adds to the growing evidence of SSB tax benefits,” they wrote in an editorial alongside the study.

Relying on Policies with Little or No Effect

The experiment with SSB taxes will continue. More data will accumulate. But it doesn’t seem wise to bet the health of future generations on the possibility that a big effect will show up down the road. The U.S. has been cutting sugar consumption from SSBs and all other sources in a big way for two decades now. Obesity rates just kept going up.

Public health advocates would be smart to pay attention to signals that this cherished policy might have no effect on population health. The time may come when they need to devise plan B.

Click here for the Cawley study, here for the Gračner study, here for the Falbe editorial, and here for further perspective.

The Tax Collector, painting by Marinus van Reymerswaele / WikiArt

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March 28, 2022