"This is the worst day of my life," Bart Simpson complains at one point in The Simpsons Movie.

"The worst day of your life so far," Homer gently corrects.

Youth and old age are periods of relative happiness, while middle age is something of a rock bottom. Credit:iStock

What's true for Bart is true for most of us under the age of 50 or so, according to a new analysis of life satisfaction encompassing seven massive surveys and 1.3 million randomly sampled people from 51 countries.

Happiness, those surveys show, follows a generalised U-shape over the course of a life: people report high degrees of happiness in their late teens and early 20s. But as the years roll by people become more and more miserable, hitting a nadir in life satisfaction sometime around the early 50s. Happiness rebounds from there into old age and retirement.