A recent USDA study found that a "tax-induced 20-percent price increase on caloric sweetened beverages could cause an average reduction of 37 calories per day, or 3.8 pounds of body weight over a year, for adults and an average of 43 calories per day, or 4.5 pounds over a year, for children." Reihan's response:
I tend to think that some kind of soda tax is inevitable. As Alan Viard suggests, it is very tempting to tax seemingly frivolous goods, like tanning and “luxury” vehicles. I would much prefer having a simple, transparent revenue source. But stealth taxes like the soda tax are a way of keeping the headline numbers on income taxes and flat consumption taxes low. And if the soda tax really does lead to a significant public health improvement, well, who can strenuously complain? Cigarette taxes seem to have turned out reasonably well when we consider reduced levels of cigarette consumption on the part of teenagers and young adults.
I'm with Reihan on this. Sin taxes are not the same as prohibition; they just help to finance the social costs of the sin. Although I'd much rather have a small but slowly increasing tax on carbon than on soda.