ANGUS DEATON, an economist at Princeton University, argues that people are far too optimistic about their futures. Gallup, a polling firm, has asked respondents in 166 countries to rate on a scale from one to ten both how good they think their lives are at the moment and how good they expect them to be in five years’ time. A ten corresponds to the “best possible” existence, and a one to the worst. Mr Deaton’s research shows that people from virtually every region of the world believe their lives will improve a lot in the near future.

Attitudes differ by age. Younger people tend to be happier in much of the developing world, perhaps because they live in countries with fast-growing economies. A very different pattern can be observed in rich countries, where both younger and older people tend to be happier than the middle-aged. Among all the demographics Mr Deaton examined, only older people living in the rich world expected their lives to worsen. Nonetheless, the differences in happiness between age groups pale in comparison with those between countries. In other words, people generally do not become happier as they age—which means that most people who believe they will be happier in five years are likely to be disappointed.