Why it pays to have a younger, smarter wife

Forget impressing her with candlelit dinners, romantic weekends away and endless compliments.

The secret to a happy marriage is as simple as choosing a wife who is smarter than you and at least five years younger.

Scientists have developed a distinctly unromantic formula to predict how compatible a couple are, based on their ages, education and relationship history.

Most likely to last the distance are couples in which the woman is more educated than the man. He, however, should be five or more years older than her. And neither should have been divorced in the past.

The finding predicts a healthy future for pop star Beyonce Knowles, 28, and rapper husband Jay-Z, 39. Jay-Z is clearly older but she has the better education, as her husband did not gain a diploma at high school.

But the research might be less popular with Michael Douglas, 65, and his 40-year-old wife Catherine Zeta-Jones.

While they satisfy the age gap, they fail on another factor. The study found that a relationship is more likely to fail if one partner has a history of divorce - and this is Douglas's second marriage.

Academics, including Dr Emmanuel Fragniere of the University of Bath, studied interviews of more than 1,500 couples who were married or in a serious relationship. Five years later, they followed up 1,000 of the couples, to see which had lasted.

From this they were able to tease out the factors that create a dream marriage - and those that doom a romance to failure.

With age, they found that if the wife is five or more years older than her husband, they are more than three times as likely to divorce than if they were the same age.

Couples in which the husband is the elder by at least five years are least likely to part, the European Journal of Operational Research reports. A good education boosts a couple's chances of staying together, and the future is particularly bright if the wife has the most studying under her belt.