Dear Economist,

I have the habit of setting my watch five minutes fast. This fools me into avoiding being three minutes late for meetings, or the train – well, more often than not – and instead being two minutes early. But if I am a rational economic agent, how do I succeed in fooling myself so systematically?

Yours (in haste),

Mark, Oxford

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Dear Mark,

That is a big “if”. Economists frequently explain eccentric behaviour with a model of two rational agents in one body, battling to outwit each other.

In your case, one agent (the one who is always late) is impatient: the risk of missing a train in half an hour is unimportant compared with the instant satisfaction to be derived from having one more sip of coffee.

Your more patient half disagrees. There seems to be some sort of stickiness in your perception of time. Stickiness is a feature of retail prices, because retailers will absorb a certain amount of inflation before spending money on repainting signs and reprinting catalogues. However at some stage - perhaps a five or 10 per cent increase in the price level - the fixed cost of that reprinting must be paid.

Your impatient self clearly suffers from a similar fixed cost of carrying out subtraction. If your watch was, say, 47 minutes fast, this fixed cost would have to be borne every time you looked at it, because being 47 minutes early for everything is even more costly than having to perform mental arithmetic. Five minutes, like a 1 per cent increase in the price level, is more tolerable.

To summarise: you have a split personality, a warped view of time and are too lazy to do simple sums. Now put down this magazine: I suspect you are running late for something.

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