Boys under the age of 12 wear their trousers around their natural waist — because most of their clothing is bought for them by their parents.
As they enter their teenage years, waistbands plunge a full five inches towards the apex of the hips as a sign of rebellion, a survey suggests.
They plummet to below the hips at the age of 16 as young men imitate rappers and gangsters by letting the crotch of their jeans dangle around their knees, with several inches of underpants on show.
The study found that waistbands slowly begin to creep up an inch or two as a man leaves his teenage years behind and enters the workplace.
By the age of 27, a chap of average build will probably wear his waistband actually around his waist.
But at 39, it begins to rise again and by 45 it will be at least two inches above. This figure increases significantly past 50 — Simon Cowell's current age — to a peak of five inches by 57. This is just seven inches below the armpits.
As pensionable age approaches, men's waists shrink, allowing them to lower the height of their trousers. By 65, waistbands are three inches above the natural waist, and by 75 only an inch, although very few men ever return to the neutral position.
Paul Baldwin, director of menswear at Debenhams, which carried out the research, said: "Our findings are very important because the position of the waistband determines how men's trousers are tailored."Our hardest task continues to be persuading men to confront the fact that their waistbands have risen. They still prefer to assume their trousers no longer fit because their legs have suddenly grown."