Is 50 middle age or 'middle youth'?

Princess Royal (50), Cherie Blair (45), Helen Mirren (55)

Women in their forties and fifties are enjoying a higher public profile than perhaps ever before. However, is so-called "middle youth" a demographic reality or just a marketing myth?

"One would have though after reaching the age of 21, age becomes irrelevant. You're as old as you feel," the Princess Royal, now embarking on her sixth decade, told the BBC.

The Royal baby boomers have grown up

The Princess seems to be articulating the thoughts of many of her baby boomer peers.

Those born in the immediate post-war years have had a dramatic effect on industrialised societies.

Rutgers University academic Helen Fisher once likened the now ageing generation to a hefty meal passing through a snake, 'changing culture as they grow older'.

They revolutionised adolescence, spawned the 60s counterculture and bought into 80s consumerism. So are today's 40 and 50-year-olds about to turn established notions of middle age on their head?

Some 80% of the nation's wealth now resides in the hands of those aged 45 and over. This age group also constitutes two-thirds of the working population, according to the Chartered Institute of Personnel and Development (CIPD).

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Businesses ignoring the power of the "grey pound" - even if only greying at the temple - do so at their peril.

The recent woes of American clothing retailer Gap have been blamed on its decision to concentrate on young consumers, alienating baby boomers.

Don't think sales of pipes, slippers and tartan shopping trolleys will rocket though. Forty (and 50 for that matter) is no longer the gateway to old age, but a staging post in so-called "middle youth".

Nowhere is the existence of this new order more obvious than on the middle shelf of your local newsagent. Glossy women's magazines are battling hard for the minds of the Princess Royal's contemporaries.

The stereotypes of middle age are being challenged

The newest kid on the block is the BBC's Eve magazine. Editor Gill Hudson, a baby boomer herself, says her readers are unwilling to conform to stereotypes based on their age.

Ms Hudson says women of her mother's generation hit middle age and adopted a uniform of "cylindrical figure, crash helmet perm and crimplene suit".

"We're not going to turn into the frumps our mums were."

However, a designer wardrobe and a gym membership are not what middle youth should be about, says Ms Hudson.

"Helen Mirren is always held up as a role model: 'Isn't it amazing a woman can be sexy at 50!' It's a cliché. Judging women only on their looks has gone on too long.

"Women this age are whatever they want to be. Captains of industry, first-time mothers, whatever."

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With figures from Madonna, through Cherie Blair, to the Princess Royal, forty and fiftysomething women don't seem to lack role models.

Dinah Worman, an advisor on equality and diversity at CIPD, says this is partly because of the sheer size of the demographic group.

However, social changes that have allowed women more control over their careers and home life have also played a hand.

"But we need more role models and to make sure more positive images are portrayed to combat the many negative perceptions which exist about ageing."

Baby boomers falling foul of "downsizing" and recruiters' ageism - particularly in the achingly young dot.com sector - is not the whole picture.

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At the other end of the spectrum, the UK Government fears the generation may opt for early retirement en masse - plunging the nation into a tax and labour crisis.

Whether the politicians will have much luck convincing this generation to work on into their 60s and 70s is debatable, considering the power baby boomers wield at the ballot box.

What is certain is that there's strength in numbers. If those of the Princess Royal's vintage say they're as old as they feel, who's going to argue?