Les Binet and Sarah Carter get a little bit angry about some of the nonsense they hear around them… like stereotypes about grandparents.

A few months ago, we were talking to some people in qualitative research groups about family holidays. The respondents were bemoaning the industry practice of raising prices when children were off school. They talked about the difficulties of taking time off work to cover the long summer weeks. They exchanged ideas about keeping the children amused and entertained on a budget.

Nothing surprising there you might think. But there was. Because these women and men weren't parents. They were grandparents. And as they chatted, it became clear that a sea-change is occurring under our marketing noses. But it's one that seems to have slipped the notice of those of us charged with understanding the world we live in.

We seem to have (belatedly admittedly) caught up with the idea that men do housework, and shop for and cook food. And as evidenced by a rash of recent dad and child ads, we seem to have stumbled upon the fact that dads now look after kids too.

But when it comes to grandparents, where are they all? When did you last see mention of grandparents in a marketing plan? When did you last write about grandparents in a creative brief? And when did modern grandparents last feature in any advertising campaign?

Because the facts regarding this silent tidal wave of grandparental change are truly startling. Cast aside your stereotypical grey-haired grandpas with walking sticks and grandmas busy knitting.

In the UK, while the average age of having a first child rises, the age at becoming a first-time grandparent is falling – to just 49 years now. One in five people in the UK are now grandparents, and will be so for 35 years (compared with 14 years as an adult with no children and 22 years as a parent with a child living at home). The number of UK grandparents will increase by a quarter by 2020… by which time one in three people will be one. Far from sitting around knitting or doing crosswords, 23% of UK grandparents are now currently in full-time employment.

The story is the same around the developed world. There are 65 million grandparents in the US (growing at twice the rate of the US population as a whole) And they fit their jobs and lives round serious amounts of childcare to help their sons and daughters to be able to work. Not surprisingly, this trend has sharply increased since the recession. One in 14 US children now live in households headed by their grandparents and nearly one million are now being raised solely by their grandparents. Apparently, children's playgrounds now feature at some US retirement complexes, reflecting this new reality.

Across Europe, we see the same pattern – 40% of grandparents in 11 European countries now provide regular childcare for their offspring's children.

Employed, active and often with more disposable income (and time) than parents, this new breed of grandparent represents an untapped opportunity for brands ranging from food, toys, and children's health to holidays. So why, we wonder, does our industry seem to have closed its eyes to one of the biggest sweeping demographic shifts affecting the lives of millions of potential customers?

Maybe it's another manifestation of our industry's preoccupation with 'youth'? Perhaps it reflects a sense that demographics are somehow 'old school' now? (In our early careers, the study of demographic trends was standard planning fayre – strategy documents regularly started with demographic influences on a brand and market). Or maybe it's simply another casualty of today's preoccupation with new digital opportunities – blinding us to these profound structural changes in our societies? Although grandparents are, in fact, very active online too. But that's another myth to bust…