What's the formula for the perfect marriage?

IF YOU thought the secret to choosing a lover who will last a lifetime was down to chemistry, then think again. According to new research, the best way to tell if a marriage will go the distance or fall at the first hurdle is by trusting another science altogether – mathematics.

Keen to rid society of the blight of divorce, mathematicians assessed the staying power of 1,074 Swiss couples and came up with a formula for a long-lasting union. Ditching such airy-fairy notions as love, romance and sexual compatibility, they used the "linear assignment model" – a methodology used by businesses to match workers to appropriate tasks – to "optimise spousal allocation". Yes, that means helping people end up with the best possible partner.

The results were dramatic. Having assessed the age difference, cultural and educational background and divorce history of all the couples, the academics found the marriages most likely to succeed were those in which the woman was five or more years younger than her partner, and also better educated.

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Couples in which the woman was more than five years older than the man were three times as likely to split up as those where both partners were the same age. And those in which the woman was more than five years older, neither partner was well-educated and one had a previous divorce, stood the least chance of surviving.

The study is good news for Beyonc Knowles and rapper Jay-Z – (she's 11 years younger and, unlike her husband, has a high school diploma). And it may explain why Madonna and Guy Ritchie had to call it quits (although she was a straight-A student, while he struggled with dyslexia, she is a whopping ten years older).

But what about Gwyneth Paltrow and Chris Martin (Gwyneth is five years older; he has a degree in ancient world studies while she is a university drop-out) or Richard and Judy (she's eight years older, but went to university, but he didn't)? How on earth are they managing to keep their marriages intact in the face of their mathematically proven incompatibility?

These mismatched couples are not alone. In fact, the study – published by the European Journal of Operational Research – concluded seven out of ten of the people involved were in the wrong relationships and would benefit from what they called "reallocation", partner-wise.

"Being able to choose our partners in the way we do is a bit of a luxury," says Emmanuel Fragnire, a lecturer in management science at Bath University and co-author of the report. "As recently as a few decades ago, marriages were a matter for the community. We know divorce has an economic, social and psychological cost, so why not try to improve the odds of a marriage succeeding?"

But is a mathematical approach to dating really more likely to improve the odds of a successful marriage than a sociological or psychological one? And can immutable facts such as age difference or educational background really do more to keep a relationship afloat than empathy, tolerance, compromise and a healthy sex life?

Fragnire makes no apology for looking beyond the factors usually credited with keeping love alive. "It appears that men and women 'choose' their mates on the basis of feelings of love, physical attraction, similarity of tastes, beliefs, attitudes, and shared values," he says. "All of these determinants are supposed to help them be happy together. However, research has shown that the longevity of marriages or partnerships also depends on objective attributes such as differences in age, family history, and educational levels.

"We imagined what it would be like if you had a regime like in North Korea, say, and marriages could be coordinated by a central agency. After looking at the impact of age difference, and cultural and educational background, we reallocated around 68 per cent of individuals to a new couple that we posited had a higher likelihood of survival."

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It all sounds a bit Brave New World. But could it perhaps throw light on some of the great love affairs of history? If only Cathy had been just a couple of years younger, might she and Heathcliff have escaped from the gloomy Yorkshire moors and settled down to a life of domestic bliss in a town house in Kensington? If only Anne Boleyn had stuck in at school, could she have kept her head?

The notion that husbands should be older than their wives goes back centuries and spans several continents, although most cultures believe there should be a limit to the age gap. (In the West, one theory has it that the women should be no less than half her partner's age plus seven).

The tradition probably stemmed from the expectation that a man would be able to provide for his wife and future family. "It is received wisdom that men choose younger women for evolutionary reasons, because they look like better breeders," says Barbara Bloomfield, a counsellor with Relate and an author of books on love and dating. "But then, of course, they may trade off looks for kindness and intelligence." Equally, received wisdom says men look for women of lower social or educational status so as not to feel threatened.

A study carried out by Aberdeen, Glasgow, Edinburgh and Bristol universities in 2005 found that the likelihood of marriage increased by 35 per cent for men for each 16 point increase in IQ, whereas for women, there was a 40 per cent drop for each 16 point rise, suggesting either that men aren't interested in clever women, or that clever women have no interest in getting married.

So why do relationships where the woman is better-educated stand the best chance of survival? "As a counsellor for 14 years, I have found that women do tend to set the emotional bar," says Bloomfield. "They are far more likely to divorce men than the other way around, so you could hypothesis that maybe better educated women make better choices."

The seven-year age gap between Elizabeth Taylor and Richard Burton may in part be responsible for their enduring attraction to one another, while their history of divorces (two of them from each other) may have been responsible for driving them apart.

Back in the real world, Alastair and Lindsay, who live in Glasgow and have been together for 12 years, married for six, and have two young children, may have the X factor, according to Fragnire.

At 39, Lindsay is six years Alastair's junior, and she has two degrees compared to his one, so is arguably better-educated. "A man is not ripe for marrying until he's past 30," says Lindsay, a fund-raiser for a major charity. "When I was in my twenties, the men my age were exploring the world. They weren't looking for commitment and settling down."

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She believes women have always matured more quickly, but that men do benefit from their partner's superior intelligence. "There was a study recently that suggested that if men wanted to live longer, they should marry a smarter woman, but that's just because a smart woman will make sure they don't eat pork pies all the time," she says.

Alastair, who works in the media, concedes Lindsay is more highly educated – "even her answers to your questions are more intelligent," he quips. But, he says, it can be useful to have a smarter person around. "Lindsay is quite subtle with her intelligence, she knows what lines not to cross and she never belittles me," he says. "Also, not to be immodest, but I think we are intelligent in different ways, we complement each other."

So do Alastair and Lindsay believe the academics are right? Can the success of a relationship really be predicted by using a glorified tick-list? "You can't reduce people's relationships to mathematics," says Alastair. "So much of it comes down to the personalities of the individuals."

"Yes and then there are the quirks of fate, like children," adds Lindsay. "They have a habit of throwing you a curve ball."

Fragnire – who, it has to be said, has his tongue firmly in his cheek – accepts his research is unlikely to revolutionise dating, but wonders if it could have an application in the world of internet dating. Sites such as Match.com promise you will find someone special within six months or they will give you your money back.

At Edinburgh-based Datetheuk, for example, members have myriad options for checking out their compatibility with a potential partner. They can draw up their own profiles, look at other members' profiles, rely on recommendations from the agency or suss out other people's personalities by reading messages posted on public forums.

Checking the age or educational backgrounds of potential matches is no doubt part of the process – but it probably comes second to that first glance at the potential suitor's photo.

A more obvious problem with the report is that it fails to take couples' happiness into account. Not all long-term married couples are happy with their lot, after all. "It was not one of the criteria we included, but it might be possible to develop the model further and include some psychological criteria, and then, I suppose, happiness could be included," says Fragnire.