Why Polls Can Matter with Sin Taxes

October 15, 2009

Opinion polls usually don’t (or shouldn’t) carry much weight when determining the best public policy—and with good reason. Policy based off populism can get society the worst results.

But when rebutting one argument for sin taxes, polls can be meaningful. Take a justification of paternalism for soda drinking, reiterated in a New England Journal of Medicine article:

A second [market] failure results from time-inconsistent preferences (i.e., decisions that provide short-term gratification but long-term harm). This problem is exacerbated in the case of children and adolescents, who place a higher value on present satisfaction while more heavily discounting future consequences.

First, this is a separate argument than one claiming asymmetrical information in the soda market—as when people are unaware of how unhealthy soda is (some might seem like they have time-inconsistent preferences but these preferences are from a lack of information). A pure claim on the time-inconsistency of soda drinkers assumes people know that soda is unhealthy but they still drink it. They discount their future “too” much. Some people make mistakes when drinking soda and the problem is that they cannot stop making mistakes. This requires paternalism that should be a relief to out-of-control soda drinkers.

So how can we know if someone is helpless against soda? Sales of soda only reflect what people desire. But time-inconsistency says that this isn’t so important. What is important is what one desires to desire. What one desires to desire is arrived at by stepping back and evaluating present and future selves rationally. And that decision should be respected. A poll can do this. Just ask a soda drinker: do you think you should be forced to drink less soda?

There have been polls for soda taxes. A January poll reported that 70% of Americans oppose a national tax on non-diet soda. But this poll might not be asking the right question to the right people to determine a time-inconsistency problem. The right poll would target only soda drinkers and ask them the question above. Otherwise pollsters pick up on useless information (for example, soda drinkers who have a time-inconsistency problem but do not want to penalize others for it).

A majority as strong as 70% suggests Americans don’t think they have a soda problem. So the time-inconsistency argument isn’t believable. What’s the believable benefit of soda taxes? You do the calculations.


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