IT IS a cliche of sex and sexuality that each new generation shocks the last.
Since time immemorial society has been constantly becoming more liberal, having more sex, with more people and in more outlandish ways; leaving the generation above clutching its pearls and expressing horror at the debauched youth they have raised.
Edwardians shocked their Victorian parents with open marriages. Then they became scandalised themselves by their own children who became the first generation in the sixties to make the contraceptive pill mainstream. Then the mid-century enfant terribles later became parents themselves and were shocked by LGBT identities in the 1980s and 1990s.
Millennials, however, are reversing this trend as one of the first generations on record to actually be having less sex than their parents did at the same age.
Millennials, or Generation Y, are the generation which reached young adulthood around the year 2000. A number of characteristics mark them out: They are saddled with student debt, they came of working age amid a crashing world economy and they use the internet with greater intensity than any other age group. Another characteristic which is increasingly defining them however, is this- they aren't really having much sex.
A recent US Government study found that just 44 per cent of teenage girls have had sex, compared to 58 per cent 25 years ago. For boys, a similar pattern emerged, with 47 per cent having had sex, compared to 69 per cent among their parents when they were at the same age.
In another study, Dr Jean Twenge from San Diego State University and author of 'Generation Me' which examines millennial culture, found that millennials are not only less likely to have had sex, but have fewer sexual partners than their parents' generation at the same age.
Data source 'Changes in American Adults' Sexual Behaviour and Attitudes 1972-2012'
She told The Independent that a unique mix of social circumstances could be causing the social shift for millennials. Following the financial crash, millennials work longer hours, in less secure work and are more likely to live with flatmates or family members amid soaring rents. She said: ". When you're a young adult living with your parents, it's harder to have sex. Even though the recession is over, more young adults are still living with their parents. It's like being a young teen again, trying to figure out where to get some privacy.
"Having flatmates can make this difficult too - you're afraid they will hear your activities, and they might not appreciate having someone else in their space. It's also more difficult because fewer young men have jobs, and most young women want to date someone who is employed."
Dr Twenge suggests digital overload among tech-addicted millennials may be another contributing factor: "I suspect some of this is connected to the rise in digital communication, including online pornography. There have been cases in the media of some young men saying that pornography has made it difficult for them to have sex with a real woman."
Rebecca Reid is a journalist and Telegraph columnist writing about sex and relationships. She told The Independent she thinks it may not necessarily be the case that millennials are less interested in sex than generations before, but rather that they are more likely to have sex in different ways which social science data may not pick up.
She said: "I think we're having sex differently rather than less, and the lines of what sex actually is can be a little blurry. Millennials are certainly more likely to experiment, and particularly to have sexual contact with people they find attractive rather than a specific gender. LGBTQ sex particularly can be more difficult to define, as penetration doesn't always occur.
"I think the easy availability of sex toys and porn is also a factor: if you're feeling sexually frustrated you've got a much better outlet to address the issue yourself, rather than going out and looking for sex."
She adds that it may be the case that people are having the same amount of sex, just with fewer people. She says: "I'm not fully convinced that we are having less sex than our parents. I think it's probable that we're having fewer sexual partners, rather than less sex per se, which I imagine is partially due to growing up in a post HIV generation who are nervous about the dangers of sex."
Other possibilities could be that bravado and stigma about not having 'enough sex' meant young people were previously exaggerating or puffing up their sexual histories to researchers and this has now stopped amid lessening shame, thereby indicating a drop in the data where more honest and accurate answers are emerging.
Regardless of the reasons, research suggests the trend is here to stay for now at least, with data plateauing at these low levels and no return spike yet emerging. It is unknown how this could shape birth rates, social cohesion and emotional and social development for this generation and wider society for years to come. Dr Twenge says: "It's not just people in their twenties, fewer teens are having sex, so I would expect that this trend will continue."
Update your news preferences and get the latest news delivered to your inbox.