I have to say, I love a good Fisking, or to Canadianize that, a Frumming. On TCS, Radley Balko takes on David Frum's National Review column on obesity and taxes. It's a good read in its entirety, but I thought it would be fun to summarize anyway, to show how each argument was demolished.

Frum argues:

1. Canadians are less obese than Americans
2. Portion sizes are smaller in Canada than in US.
3. It's because Canadians are less wealthy that portion sizes are smaller.
4. Smaller portions lead to less obesity.
5. Obesity leads to health care costs.
   
6. Making sodas more expensive (by taxation) will cause lower consumption of sodas (conclusion: also reduce obesity, also reduce health care costs).

Without facts, one might follow that logic. Balko, however, demolishes one after another of these, showing how much of a house of cards that logic was:

1. Canadians are similarly obese to Americans and Frum's evidence was only anecdotal.
2. Portion sizes are similar and Frum's evidence was only anecdotal.
3. Since portion sizes aren't smaller in Canada, wealth isn't a factor in portion sizes (at least the wealth difference between CA/US doesn't matter to that). Also note that total consumption of caloric sodas has been steady for decades as Canadians have gotten significantly richer (and soda cheaper).
   
4. This one requires more data to completely demolish, but the evidence that total consumption of caloric sodas has been steady for decades does cast doubt on the idea that smaller cans of sodas will reduce consumption.
   
5. There's more evidence that poor fitness (sedentary lifestyles) has a much greater health care cost than obesity.
6. Such a small increase in price of soda is unlikely to change consumption, given that consumption has been steady for decades as soda production has gotten cheaper and people richer.
   

Balko doesn't point this out, but soda doesn't appear to be very price sensitive. Rather than buying cheap store-brand sodas the market overwhelmingly goes to the higher-priced image brands.