It is a thousand years ago somewhere in Europe; you are one of a line of ten thousand men with spears. Coming at you are another ten thousand men with spears, on horseback. You do a very fast cost-benefit calculation.
If all of us plant our spears and hold them steady, with luck we can break their charge; some of us will die but most of us will live. If we run, horses run faster than we do. I should stand.
Oops.
I made a mistake; I said “we”. I don’t control the other men. If everybody else stands and I run, I will not be the one of the ones who gets killed; with 10,000 men in the line, whether I run has very little effect on whether we stop their charge. If everybody else runs I had better run too, since otherwise I’m dead.
Everybody makes the same calculation. We all run, most of us die.
Welcome to the dark side of rationality.
This is one example of what economists call market failure — a situation where individual rationality does not lead to group rationality. Each person correctly calculates how it is in his interest to act and everyone is worse off as a result.
David D. Friedman, “Making Economics Fun: Part I”, David Friedman’s Substack, 2023-04-02.
October 11, 2023
QotD: A rational army would run away …
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