Sex File: How often should we make love? 

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I know it might sound unromantic, but my husband and I have been trying to work out what the ideal amount of sex in a relationship is. We're busy but really value sex for the sake of our relationship and wellbeing. Is once a week a good aim? We're in our 30s. We don't have children and we've been together for ten years.

People are rarely honest about the amount of sex they are having. As a result, everyone ends up assuming that other people are at it like rabbits. In 2017 the global market research company Ipsos confirmed this misperception by conducting a survey that asked people to estimate the frequency with which men and women aged 18 to 29 had sex. The men in the survey guessed that women aged 18 to 29 had sex 23 times a month, and the women guessed that the men had sex 13 to 15 times. Both estimates were, I suspect, wildly out, but they indicate how distorted our perception of sexual frequency has become.

Bigger academic studies provide a much better, more realistic benchmark for the frequency of sex. The UK National Survey of Sexual Attitudes and Lifestyles is conducted every ten years and involves more than 15,000 participants. The most recent one (Natsal-3) was completed in 2012 (so we are due some new data soon) and the findings show a steep decline in the amount of sex that people in Britain are having; less than half of men and women aged 16 to 44 were having sex once a week.

The Natsal study uses median figures, to eliminate the small number of outliers who report having sex hundreds of times a month. The median number of occasions of sex in the past month among women aged 35 to 44 was just two. For men, the median figure per month was three. Only 13.2% of women and 14.4% of men had sex more than ten times a month, and among 35 to 44-year-olds 27.2% of women and 23.1% of men reported having had no sex in the previous month.

You will probably find that data reassuring because it means that you and your partner are doing better than most. Once a week is a perfectly reasonable frequency, and research by Dr Amy Muise, a sexuality and relationship researcher at the University of Toronto in Canada, suggests that it might even be the optimum. In 2015 she examined the relationship between sexual frequency and happiness, and found that people who had sex less than once a month were less happy than those having sex once a week. But, interestingly, having sex more than once a week didn't bring about a corresponding increase in happiness.

In the same year George Loewenstein, a professor at Carnegie Mellon University in the US, ran a small study that tested this phenomenon. He asked 32 of 64 married couples to double the amount of sex they had and to respond to short daily surveys about their level of happiness. On average the couples in the trial group increased their sexual frequency by about 40%, but it didn't make them any happier - it had the opposite effect.

Ultimately, when it comes to sex, quality is more important than quantity. So much of human sexual behaviour isn't about the physical pleasure that is derived from the actual act of sex. It is about the emotional connection that sex facilitates. Sex is a way for couples to validate their relationship and to reassure one another that they still find each other sexually desirable and loveable. That is important at any age, but it is even more so in long-term relationships. As people get older, fatter, balder and more exhausted, it is the deeply embedded connection between sex, love, comfort, trust and reassurance that keeps their physical relationship alive.

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