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I’d like to talk a little about science and data, for those of you out there who really want to believe that they are objective measures of reality. You may believe that because someone you trust told you so and it sounded nice and reassuring. I’m sorry to tell you that, in the words of the great Ben Goldacre, I think you’ll find it’s a bit more complicated than that.
I’m thinking of all this because I recently saw a science news article proclaiming that people in Philadelphia are drinking less soda after instituting a tax on sugary beverages. This is ostensibly a success, since the tax was put into place to do precisely that, since sugary beverages are making us fat, and being fat is unhealthy.
Several of the things I’ve just said are wrong, and several are right but pointless and out of context. Let’s go over it.
First of all, it’s not actually a tax on sugary beverages, nor is it a “soda tax” as it’s known colloquially. It’s a tax on any beverage that’s not water, milk, fruit juice, or vegetable juice, which is on its face stupid because milk, fruit juice, and vegetable juice can make us fat while my precious Coke Zero cannot do so on its own because there are basically no calories in it. Meanwhile, alcoholic beverages are taxed in their own category, and let me tell you, they are definitely making us fat.
Of course, stopping people from getting fat isn’t the only reason the tax was implemented. Philly representatives claimed that the increased tax would go to education for very young children, which is hard to do if you’re claiming that the tax will also force sales to go down. If you raise the tax by 20% but then 40% of people stop buying the product, have you made any money? Show your work.
Before: 100 people pay $1 in tax. Result: $100. After: 60 people pay $1.20 in tax. Result: $72. Something isn’t working, here. What could it be?
Now let’s talk about the actual study. Their data shows that 40% of people are less likely to drink a soda and 60% less likely to drink an energy drink. Why are the numbers so shady? Because it was a survey, not a look at actual numbers. So already, we have to realize that data isn’t just data — it’s been collected in a particular way that means that it may not mean what we thought. Maybe people just say they won’t buy soda but then they do.
To be fair, some actual numbers do suggest that soda sales have gone down in Philly, including one that says it may be a nearly 60% drop. But we don’t know if they’ve gone up in the areas just outside of Philly. Poor people may not be able to drive to the edge of the city to pick up their soda, but others might.
Back to the study: about 60% of respondents said they’d be more likely to buy bottled water. Is that the change we want? Yes, water is what everyone should be drinking all the time, but not out of wasteful plastic bottles. The tap water in Philly is clean and there’s no reason for people to buy bottled water, so this is actually a negative side effect of the tax.
Here’s another possible negative side effect that isn’t mentioned in the study but has shown up in other studies: alcohol sales in Philadelphia have increased since the soda tax went into effect. This has been found in other places like the UK, where a recent study shows that a drop in sugary drink sales correlated to an increase in lager sales.
So all of this is just an illustration to say that data isn’t just data, existing in a vacuum. Data has to be collected in a certain way, and decisions are made by humans how to collect it, and how to statistically analyze it. Data is used by humans to institute policy change, and even when that policy change may seem to work in certain ways, you need to look at a bigger picture to understand whether it’s actually accomplishing the thing you set out to do.
But seriously, stop taxing Coke Zero. It’s the only thing that keeps me going some days and you do not want me to swap it out for whiskey. Productivity here is going to plummet.