2. How much do "sugary drinks contribute to the global rise of noncommunicable diseases"? What is their share of calories in the diet? (Not much). What is the relationship between calorie intake and bodyweight? (Not simple). Between bodyweight and NCD burden? (Not what you think)
3. But even that is not good enough - you also need a counterfactual. If sugary drinks didn't exist, what would people drink, eat or do instead? (e.g. eat more chocolate), and what disease burden would that create? Then compare. A virtually impossible calculation.
4. Now add a tax to change behaviour. What is the effect on price? What is the price sensitivity of the at-risk group (fat people, presumably) - they may like sweet stuff and be less price sensitive. Is there an 'announcement effect' and then demand creeps back up?
5. What effect does soda price change have on consumption of soda and total calorie intake in the at-risk group? For example, a 20% change in 5% of daily calories is a 1% change in overall calorie intake. Not so much. How long does this consumption effect persist?
6. Are there compensating 'cross-elasticities' with other sweet stuff - do they add more sugar to tea, eat more chocolate, drink untaxed juice? Or get calories from another source? Or change behaviour e.g. walk less? What is the net impact?
7. And what is the effect of the price increase, especially on the not-at-risk group, who don't even get 'health benefits', however small? Are they poorer? Is it regressive? Why are the sugar-laden juices and smoothies of the rich spared the tax?
8. As it is a revenue-raiser, is there another tax that will be dialled down to retain fiscal neutrality? If so, which tax and who benefits? Is the net effect a transfer from poor to rich?
9. What alternatives have been considered? Rather using a tax with a second-order impact on a tiny part of the problem that mostly hits people not at risk, might it be better to focus more comprehensive support on the subset of people who are at risk and want help?
