From The Economist:
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.
As the report shows, the poor are more likely than other people to make bad economic decisions. This is not because they are irrational or foolish but because so much is stacked against them. They are more likely to lack the basic information needed to make good choices, such as which fertiliser to use or when to apply it. They are more likely to live in societies which hold mistaken or harmful views, such as that girls should not go to school.
Conventional economic thinking assumes the poor will want to earn their way out of poverty. But as studies from countries as different as Ethiopia and France show, poverty makes people feel powerless and blunts their aspirations, so they may not even try to improve their lot. When they do, they face obstacles everywhere. They have no margin for error, making them risk averse. If they do not know where their next meal is coming from, saving and investing for the future is hard.