Here’s a consumer tip, for what it’s worth

‘Suppose you bought a case of claret a few years ago for £20 a bottle. It now sells at auction for about £75. You have decided to drink a bottle. Which of the following best captures your feeling of the cost to you of drinking the bottle?
 
1. £0. I already paid for it.
2. £20 — what I paid for it.
3. £20 plus interest.
4. £75, what I could get if I sold the bottle.
5. -£55. I get to drink a bottle that is worth £75 that I only paid £20 for, so I save money by drinking it.’
 
This question (with prices in dollars) was given to readers of Liquid Assets, an annual newsletter on wine auction pricing. It was posed by Richard Thaler, later to win the Nobel Prize in Economics. The proportion choosing each answer was:
 
1. 30%
2. 18%
3. 7%
4. 20%
5. 25%
 
To an economist, there is but one correct answer to this question: by drinking a bottle of wine which could be sold for £75 you are sacrificing £75 of utility which could be used for something else.