For most goods, the two show broadly the same pattern: with small
errors, what people profess to buy grosses up to what is really being
sold in the country. But tobacco is a big exception. Less then half of
the recorded cigarette purchases shows up in the Living Cost and Food
Survey. In the US equivalent, the ratio is not even 40%.
The mismatch between what smokers say in surveys and what they do in
practice is a classic example of the difference between "stated
preferences" and "revealed preferences".
Social engineers love stated preferences. Opponents of big
supermarkets, too, always have a survey at hand, indicating that the
vast majority of residents in their areas would never set foot in a
discounter. But once it is there, it flourishes.
There is nothing schizophrenic about this behaviour. When asked
whether you would shop in a big supermarket in your area, of course you
respond something like "No! Small, local shops are much more charming and personal"
- because that is the socially acceptable thing to say. When you smoke,
saying that you want to quit makes you at least a repentant sinner.
Now ask yourself: Is voting more like a national product account - or a consumer expenditure survey?