By James Arnold
BBC News business reporter
For advertising types, the pound comes in all sorts of colours.
Older shoppers pass most modern advertising by
There's the pink pound (free-spending gay shoppers), the green pound (eco-consumers) and the recently-identified brown pound (ethnic minorities have money, marketers have discovered ).
Before all that was the grey pound - a cliché of the advertising industry since at least the 1970s, according to Reg Starkey, a veteran adman and creative consultant at agency Millennium Direct.
Every creative director knows that the over-50s - currently 20 million strong, and growing fast - hold 80% of the nation's wealth.
Trouble is, no one wants to do anything about it: according to a recent Age Concern survey, two-thirds of elderly consumers felt advertising portrays them negatively, and three-quarters simply didn't relate to it at all.
"If you see someone over 40 in an agency, chances are they're either a client or the chairman," says Jean-Paul Treguer, head of Senioragency, an advertising firm that targets the mature consumer.
It doesn't have to be this way. Nor, say advertising professionals, do agencies have to go to traumatic lengths to make their commercials appeal to a broader age-group.
In fact, a few simple rules would suffice:
Don't just entertain - inform.
There is a long-established piece of advertising wisdom that says while young people want adverts to make them laugh, older people want hard facts.
Like most wisdom, it's only slightly true. Older people are far more rational customers than the flighty young, and need serious persuasion from anyone wanting their money, but they like a laugh as much as anyone.
"Thing is, if there's a hole in an ad, they will spot it," says John O'Sullivan, chairman of MWO Advertising.
Having often more time and more patience than the young, older shoppers will research their purchases in far greater detail, says Mr Starkey. An effective advert, therefore, has to contribute to that research, rather than simply trying to push the emotional or cultural buttons that turn on the young.
Don't count out celebrities.
The use of the famous, or nearly famous, is frequently seen as the last gasp of a copywriter running short of inspiration.
Guinness's ageing swimmer spoke to the depths in older drinkers
In fact, argues Mr Treguer, celebrity role models - what he calls "generational heroes" - can deliver the goods. In France, advertisers use a range of celebrities d'un certain age, but still with some va-va-voom: Catherine Deneuve, Johnny Hallyday, former cyclist Raymond Poulidor - at 66 still the country's favourite sportsman.
In Britain, meanwhile, the market is sewn up by an small gerontocracy of actors - notably former comic actress June Whitfield, whose perennial reappearance as the face of the elderly provokes cries of despair.
"These are precisely the sorts of ads that are made by the teenage copywriters," groans Mr Starkey.
By and large, in fact, the sort of ads that old people like are the sort of ads that everyone likes - the big-budget, cinematic numbers that admen love making and companies hate paying for.
In recent years, there has been a rash of these. Pundits pick out a Ford campaign where modern cars were digitally inserted into vintage film milieux alongside Steve McQueen and Dennis Hopper.
Guinness, despite its apparent attempts to court younger drinkers, is another crossover hit, especially for its "Swim Black" spot, where an ageing strongman discovers his powers are on the wane.
"It's beautifully made, and it brings in images that speak directly to an older audience," says Martin Smith, managing director of Millennium Direct.
Remember: old people are different. Or are they?
The great debate in the industry is over whether it's worth advertising to older people at all. One camp argues that elderly consumers form their tastes early in life, and barely budge after 40 - and almost never in response to advertising. The other camp insists that the old are just as malleable and changeable as the young - they just need special handling.
Gris, moi? asks Johnny Hallyday
The second camp seems to be winning out. "Everyone has misconceptions about being old until they are old themselves," says John O'Sullivan. "Anyone who thinks we stop taking in fresh information about products when we're over 50 must be mad."
In the opposing camp is agency Young & Rubicam. In a controversial report two years ago, Y&R director Simon Silvester argued that consumer tastes are more or less set in stone by the age of 35 - a process of petrification that can be measured by a person's musical tastes.
The report has continued to cause a stir, culminating in an exchange this year via the pages of the Financial Times between Mr Silvester and Mr O'Sullivan.
Oh, and don't generalise.
Almost all of the above will turn out to be wrong.
According to the Henley Centre, traditional family patterns are now the rule in only 30% of UK households. The typical model, where children fly the nest, leaving parents to enjoy a prosperous and leisurely late middle age, may be under threat.
"Children move back home after college; men in their 50s remarry and start families," says Mr Starkey.
"Life is becoming less linear, and more cyclical."