The pleasure that women get from making love is directly proportionate to the amount of money their partner earns, new research claims.
Psychologists believe that to signal loyalty women orgasm more frequently if their man is rich. It indicates that they would be good marriage material, they claim.
They say a wealthy mate equals a more desirable mate and women demonstrate this by being more responsive in bed.
Lead researcher Dr Thomas Pollet, a Newcastle University psychologist, said: "We found that women report more frequent orgasms the higher their partner’s income is.
"It appears consistent with the view that female orgasm has an evolved adaptive function.
"It serves to discriminate between males on the basis of their quality.
"If so, then it should be more frequent in females paired with high-quality males.
"More desirable mates cause women to experience more orgasms."
There are plenty of famous examples of extremely wealthy men securing the attentions of women who otherwise seem mismatched in looks and age.
Playboy founder Hugh Hefner is in his 80s but has had a string of model girlfriends more than 60 years younger than himself.
And while American business magnate Donald Trump gets older and richer, his wives get younger.
Dr Pollet and his co-researcher Professor Daniel Nettle analysed data gathered in one of the world’s biggest lifestyle studies.
The Chinese Health and Family Life Survey targeted 5,000 people across China to conduct in-depth interviews about their personal lives, including detailed questions about their romantic lives and income.
Among these were 1,534 women with male partners, who formed the basis of the study.
They found that 121 of the women always orgasmed during sex while 408 often had them. Another 762 "sometimes" orgasmed while 243 rarely or never had them.
The figures are similar to those for western countries.
Dr Pollet said that several factors were at play but that money was one of the main ones.
"Previous research in Germany and America has looked at attributes such as body symmetry and attractiveness, finding that these are also linked with orgasm frequency. "Money, however, seems even more important," he said.
The Daily Telegraph