German and American scientists who analysed the results of a long-term British survey in which more than 21,000 men and women were regularly asked how happy they were with their lives.
They replied on a scale of one to seven, with one meaning they were not satisfied at all and seven indicating complete satisfaction.
Life satisfaction was rated about 5.5 when the subjects were in their late teens, on average.
This gradually dropped to about five when they turned 40. appiness hovered around this mark for the next few years, before taking an upturn around the age of 46.
And through their fifties and sixties they became more upbeat, with satisfaction peaking at a rating of 5.9 around 74. After that it drops off as more people become affected by health problems.
The researchers said it was possible that people become more appreciative of what they have as they get older. They may find a desire to make the most of their remaining years, they added.
Writing in the journal Social Indicators Research, they said: 'This awareness of impending mortality may lead older individuals to focus on ways to make their remaining experiences as enjoyable as possible.
'Compared to younger individuals, older people tend to place a greater emphasis on emotional aspects of social interactions and are likely to remember the emotional content of their experiences.'
But this happiness scale appears to be a peculiarly British phenomenon, the researchers from the German Institute for Economic Research found.
When they carried out a similar analysis of German men and women, they found that levels of satisfaction remained relatively stable throughout life.
The British figures chime with recent claims that the mid-life crisis is a thing of the past.
Improvements in healthcare, education and life expectancy mean 'wobbles' around the age of 40 are now less likely, psychologists claimed last month.
By that time, most will have married, bought a home and chosen a career. With those difficult decisions behind us, we are free to start enjoying life and learn from our mistakes.
Does all this chime true for you?