Poor behaviour

A BAT and a ball cost $1.10 between them. The bat costs $1 more than the ball. How much does each cost? By paying attention to how people actually think, behavioural economics has qualified some of the underlying assumptions of classical economics, notably that everyone is perfectly rational. In fact, the mind plays tricks, dividing up $1.10 (in this example) neatly into $1 and 10 cents, rather than correctly into $1.05 and 5 cents. People also tend to copy others and often prefer to co-operate rather than compete. For these reasons, some of the simplifying assumptions of economics are not always correct: people do not act in every instance in their long-term self-interest; they do not weigh up all the costs and benefits before taking a decision.

Many of the insights of behavioural economics were based on studies of American university students and other privileged folk. But they apply with greater force to the poor—both the poor in rich countries and the more numerous inhabitants of developing ones. Behavioural economics therefore has profound implications for development. The new “World Development Report”, the flagship publication of the World Bank, considers them.