BARELY a week goes by without a report on the level of confidence among consumers, businesspeople and investors. Optimism is what�s wanted�Keynes talked of the �animal spirits� that influence economic activity. Pessimists are routinely denounced as Jeremiahs. Those who try to bet on falling prices find their activities are restricted.

A cheery disposition may be necessary for societies to function. Daniel Kahneman, a psychologist and Nobel economics laureate, has a chapter in his book �Thinking Fast and Slow� which describes overconfidence as �the engine of capitalism�. No entrepreneur can be sure that his planned investment will succeed but if no one took a risk, new products and jobs would never be created. A certain blindness to the odds may be necessary. According to Mr Kahneman, the chances of an American small business surviving for five years are just 35%. But ask individual entrepreneurs about their prospects and 81% think they have a better than seven-in-ten chance of success.