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Mathematics

What you eat is how many you are

Nature volume 389, pages 16–17 (1997)Cite this article

How do people make decisions? A standard answer (not the only one) runs as follows: every individual first ranks all alternatives open to them, and then chooses the top of the list. This model had not been validated by econometric studies, but now a simple realization has changed the situation: two people don’t act the same way as one.

This picture of decision-making can very easily be cast into a mathematical model. If K is the set of possible decisions, the ranking is defined by the ‘utility function’, U(K). The individual prefers one decision over another if the value of its utility function is higher. Taking the right decision then amounts to finding in the set K the point x that yields the greatest utility U(x). In this way, every problem in decision-making can be translated into a mathematical problem.

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Figure 1: Tyrone Power tries to work out what has happened to his demand function.

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References

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  1. Ivar Ekeland is at the University of Paris-Dauphine, 75775 Paris, Cedex 16, France

    Ivar Ekeland

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Ekeland, I. What you eat is how many you are. Nature 389, 16–17 (1997). https://doi.org/10.1038/37867

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