The idea of the curse of 27 is nothing new – even if, when it comes to musicians, it is actually a myth. But for young men today, the age is cursed in another way: 27 per cent of men still live at home aged 27, compared to only 13 per cent of women.

Let’s call them the stay-at-home sons. Many of those who linger at home have little choice. Men earn an average of £1,100 less than women between the ages of 22 to 29. As women increasingly outperform men at school and university, the gap could get larger still.

Thanks to years of anaemic housebuilding, there are 600,000 more young adults, aged 20-34, living with their parents than 20 years ago. Men and women are both living at home longer. Many men, lagging behind their female contemporaries in the jobs market, just can’t afford to get out.

Men are also less likely to get hitched in their twenties: by the age of 29, women are 50 per cent more likely to be married than men. Although both sexes are marrying later than ever, women still tend to go out with, and marry, men a couple of years older than they are, and are more likely to move in with partners in their twenties.

When marriages go wrong, men are significantly more likely to return to living with their parents. Women still account for 90 per cent of lone parents with dependent children. The ONS finds that men are more likely to return to their parental home after a breakdown in a relationship.

So women earn more and marry earlier, but not by enough to explain why men are twice as likely to live at home aged 27 and later. This isn’t just about economics or love: it’s also about attitudes to living at home.

Parents do seem more indulgent of their male children lounging around at home while they are on the road to 30 than of their female children doing so, while young female adults seem in more of a hurry to leave the family home.

“I’m a mum and my boy has a very strong bond with me,” says Sue Firth, a psychologist. “If we’re typical then he’ll be reluctant to leave until he feels as loved by someone and she does everything for him the way I have! Not much incentive to leave if you have to cook, clean and wash for yourself.”

She thinks that young women tend to be, “much more independent and keen to start a life on their own”.

If parents expect daughters to leave the family home earlier than their sons, this is also a legacy of women traditionally marrying much earlier: in 1991, the average age for women marrying for the first time was just 25.

Men deep into their twenties are less reluctant to live with their parents than women are. Earlier this year, Aviva Home published a report into attitudes to living at home. It found significant differences in how women feel about staying with their parents compared with men. Women were 8 per cent more concerned about their personal space than men, and 10 per cent less likely to feel that their family home might not feel like their own than men.

Women were also more likely to say they wanted to own a home of their own “as soon as possible” – and men were more likely to describe themselves as “not bothered” about becoming a homeowner.

“Women expect to have children and know that they will have responsibility for them,” says Belinda Brown, from the Male Psychology Network. “Although this may not happen at a level which is consciously articulated, I think the fact that women know they will have children who they have to look after does motivate them to ensure they have a way of earning a living. Boys don’t know that they will have children they will have to look after.”

Pilot studies conducted by Brown suggest that male students who expect to have families tend to do better at school – and later earn more money – than those who do not.

But the male curse of 27 goes beyond basic material realities. “Boys are just doing so much worse psychologically, in school, economically, and in motivation, that parents – especially mums – are likely to feel protective of them and take them in,” says Dr Warren Farrell, author of The Myth of Male Power and Father and Child Reunion.

The rise of the stay-at-home son is also a symptom of a much wider crisis in masculinity.