Dear Economist,

Why is it so hard for me to find a properly fitting pair of trousers on the high street? As a 33-34in waisted, 5ft 11in male, I consider myself of average build. Yet appropriate attire always seems to be out of stock. Can economic theory shed any light on this?

Concerned Trouser Consumer

Dear Trouser Consumer,

The obvious economic analysis here is Harold Hotelling’s 1929 classic on product differentiation. Hotelling imagined two ice-cream stands trying to decide where to locate on a beach.

His conclusion was that they would end up side-by-side in the middle, with each customer going to the nearest stall. Similarly, major political parties tend to cluster in the centre of the political spectrum.

We do not see companies specialising in a single size of trouser; if we did, you would be swamped with pairs that fitted you well. A better explanation may be that companies are engaging in “strategic product differentiation” to avoid competition. For Hotelling’s ice-cream vendors, that would mean locating at opposite ends of the beach. For rival bus companies it would mean one service departing on the hour and half hour, the other at quarter to and quarter past.

In each case the aim is to give both companies the ability to raise prices without losing too many customers.

In your case, strategic product differentiation would mean that one clothes store offers trousers with a 32in, 36in and 40in waist. The other offers 30in, 34in and 38in.

If you are shopping at the wrong store you will never be satisfied; the right store would supply clothes to fit, but prices would be higher for lack of competition. It is a bizarre economic theory, I agree.

But it would explain your commonplace frustration.

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