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Harvard researchers conduct a real-world test of soda taxes

June 17, 2010 |  4:00 pm

Another day, another study on soda taxes.

Soda But this one isn’t based on mathematical models or unreliable food frequency questionnaires. This time, researchers at Harvard implemented a temporary soda tax in the cafeteria of the school's Brigham and Women’s Hospital in Boston. Then they waited to see whether actual people changed their drinking habits.

It turns out that they did. During a four-week period when the price of a 20-ounce bottle of soda went up by 45 cents – which amounted to a 35% price increase – sales fell by 26%. Meanwhile, sales of bottled diet soda rose by 20%. (The researchers said they were unable to change the prices of fountain drinks, so those soft drinks were not subject to the tax.)

Prices for full-calorie soda went back to normal after the test period, but sales ticked back up only slightly. Then researchers posted fliers around the cafeteria that said:

"Lose up to 15-25 pounds in one year and decrease your risk of diabetes by 1/2. Just skip one regular soda per day. For zero calories, try diet soda or water."

Those fliers remained up for four weeks, but sales of bottled soda didn’t fall during that period – in fact, they rose slightly.

Finally, the researchers reinstated the 45-cent soda tax while keeping the fliers up for another four weeks. That cut into sales of bottled soda, prompting a 36% decline compared with the weeks before the prices first changed.

The researchers concluded that taxes can work – only the price increase had a statistically significant effect on sales of sugared soda. When the tax was in place, diners switched to diet soda and coffee; sales of water and fountain drinks stayed the same throughout the study.

The researchers also wondered whether people who skipped their usual sodas would reward themselves by buying more snacks and desserts, but sales of those treats didn’t change either.

Of course, there was no way to tell whether anyone actually lost weight – or reduced their risk of health problems like obesity and diabetes – as a result of the tax.

The results were published online Thursday by the American Journal of Public Health.

-- Karen Kaplan

Photo: Higher prices encouraged consumers to switch from regular soda to diet soda or coffee. Credit: Justin Sullivan / Getty Images

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Comments (8)

This is inconclusive who profited off the raised prices of the soda? Did you tell the people they were being taxed or did you just randomly change the price?

Great for a "price theory" solution. Now, for the whammy factor that was not considered when developing study results.

How many people brought their own, when they found out that soda was only 35 cents a can (based upoin the purchase price of a 12-pack) from the supermarket?

The same stunt happened where I work and if we weren't bring our own beverages in, we set up stores / honor bars that stocked food, candy and a variety of sodas and juices.

It basically comes down to freedom of choice. Although I have been drinking water and diet drinks, for about fifteen years. I recently switched to sugar based drinks. The result over a three month period? A loss of 30 pounds and still going.

Somehow, I don't think diet sodas are all that they are cracked-up to be.

Bottom-line? Choice overrides taxes. People who want to turn this into a "nanny state" need to get a life.

LAUSD, how about restoring or providing additional funding for Youth Services activities, to get youngsters off the street and getting a work-out on the playground?

Then once people get over the ' sticker shock ' they go back to buying their ' stuff '.
A fast food and soda tax could raise billions to help this country and improve some peoples health if they give it up.

I had a 1 litre a day soda habit. I gave it up cold turkey for 4 months. Did not lose a single pound. I just got cranky.

I had a 1 litre a day soda habit. I gave it up cold turkey for 4 months. Did not lose a single pound. I just got cranky.

This is an interesting study, but I wonder if people would eventually get used to the higher price and start buying after a year or more of the inflated price. Also it seems to me people would probably just shift to the fountain-soda. I almost never drink soda, but if it comes free with a meal and I can't get a water I'll drink it.

The US government already uses our tax dollars to subsidize corn farmers who grow corn specifically for high fructose corn syrup. This is why sugared drink relatively inexpensive in the first place. Now, there are groups out there trying to convince the government to add a tax to sugared drinks so we buy less of them. Doesn't this seem completely ludarcris?!
Maybe we should stop subsidizing corn that can not be used for food and is only suitable for high fructose corn syrup. Just a thought.
We should all realize taxing vices doesn't work. Consider smoking. Most smokers didn't quit when taxes were hiked. They just paid more. Which leaves one to wonder where all that tax revenue is going.

Puts a tear in my eye to see the Coca-Cola that all Americans love is now being taxed even more just to fuel the nanny state. Fight against this by joining the Nanny State Liberation Front on Facebook!!!!


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