The soda tax tells us what we can't do. That's not a good way to change bad behavior.

The state of the universe.
June 1 2010 9:51 AM

Why the Soda Tax Makes Us Angry

Higher prices are bad. Being told what to do is worse.

In 1972, the residents of Miami lost their minds. That's how it seems, anyway, when you learn they were stockpiling laundry detergent. There was no shortage, but still they rushed to stores to grab as many boxes as they could, even purchased it from other counties. What turned all these people into clean freaks overnight?

Miami was one of the first cities in the country to ban the sale of detergents containing phosphates, chemicals that increased cleaning power but also increased the growth of algae when drained into the water supply. The algae could suffocate plants and animals and, in some cases, produce neurotoxins. The rule made a lot of sense, and it didn't cause any inconvenience because other equally effective additives such as carbonates were available. And yet, people went out of their way to procure the banned substance—even if it meant breaking the law to do so.

Like the rest of us, the Miami launderers didn't want to be told what not to do. We value our freedom of choice so highly that when it's threatened by an external authority, we automatically rebel in order to reassert control. We end up wanting whatever the authority says we're not supposed to want or have. Psychologist Jack Brehm coined the term reactance in the 1960s to describe this phenomenon, but we've long known the attraction of forbidden fruit. In one classic study of reactance,researchers placed signs in several of the restrooms of a university, either politely asking people not to write on the walls or ordering them, "Do NOT write on the walls!" How did people react to the latter? They were more inclined to write on the sign itself in defiance (e.g., "So what are you going to do about it … [expletive deleted] … You'll never catch me. Ha! Ha! Ha!"). Sometimes they skipped straight to stealing the sign. In other words, a minor prohibition elicited a major reaction—and what was true in the 1960s is just as true today.

It should come as no surprise, then, that we have a problem with "sin taxes," such as the penny-per-ounce surcharge on sweetened beverages championed by CDC Director Thomas Frieden. Most of us would probably agree that we'd be better off if we drank less soda, but any government action designed to control consumption puts us on alert. A tax is far less likely to induce reactance than an outright ban, but we feel queasy whenever we think The Man is trying to influence our behavior. In the case of the sugar-sweetened-beverage tax, which has often been referred to as a "fat tax," our discomfort is greater because the measure seems to encourage finger-pointing. In defense of the proposal, New York Gov. David Paterson has said, "Someone has got to contribute to the $7.6 billion the state spends every year to treat diseases from obesity."Those who are not obese may feel that they should not have to pay for the "sins" of the fat people over there, the ones creating the problem. Those who are obese are likely to feel shamed and persecuted. And we all recoil at the thought of the government trying to regulate our bodies.

Most scientific evidence suggests that an increase in price does lead to a decrease in consumption. For soda, it's estimated that a 10 percent markup would reduce intake by about 8 percent (PDF). (Assuming that a 12-pack of soda costs $5, a penny-per-ounce tax would raise its price by $1.44, or about 29 percent.) However, much of the research looks at the impact of higher price without taking into account that consumer response may vary depending on the reasons given for the markup. When the markup is presented specifically as a way to modify behavior, it is likely to elicit reactance and therefore be less effective. In the real world, people's desire to assert their freedom to drink soda may very well trump the disincentive of higher cost.

In an ideal situation, the price of soda would creep up without any government intervention, naturally resulting in less consumption. That's not likely to happen, so if we want to encourage people to drink less soda, we need to figure out how to force a raise in price without inducing reactance. One oft-proposed solution is to cut the corn subsidy, increasing the cost of high-fructose corn syrup and, therefore, of production. Well, that's not likely to happen either, and even if it did, soda prices would rise by, at most, 2 cents per can, not enough to affect consumer behavior in any substantial way.

Perhaps the best option is to reframe the tax so it doesn't smack of moral policing or prompt grumblings about Big Brother. As William Saletan wrote last year, this is not just a health issue: "[I]sn't it a matter of personal choice? Doesn't taxation to control people's eating behavior cross a fundamental line of liberty?" It's common practice to publicize the long-term social benefits of a policy in order to increase public support for it, but when it comes to the soda tax, this practice calls attention to what people perceive as an affront to their personal freedoms.

Gov. David Paterson and New York City Mayor Michael Bloomberg both support the tax. They have spoken of it mostly as a way to reduce consumption and to pay for the medical costs of obesity. But recently, when trying to garner support for the tax, Bloomberg emphasized that it was a quick and effective way to generate much-needed revenue for the city. He spoke of the tax as an "easy fix" that would "keep thousands of teachers and nurses where they belong: in the classrooms and clinics." This framing makes the tax seem like any other, instead of one specifically designed to control behavior. So while it may still face opposition because it's a tax and we hate taxes, it sidesteps the problem of reactance.

New Yorkers also show more support for the tax when told that the revenues would be used for the prevention of childhood obesity. In this case, the focus is on providing new choices through obesity-prevention programs rather than on taking away the choice to drink soda. Even though the goal is still to manage behavior, the approach seems more encouraging than prohibitive. Since reactance is stirred whenever we perceive loss of control, proponents of the tax must choose their words very carefully.

If we want to implement a sweetened beverage tax and maximize its effectiveness, the best approach would be to dissociate it from the larger issue of individual choice and focus on its immediate practical benefits, such as the revenue it produces. Over time, we'll get used to it. We might even wonder why we didn't do it sooner.

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Sheena Iyengar is a professor at Columbia Business School and the author of The Art of Choosing.