The behaviour of this nation, its relentless heeding of expert advice, the stiff downward curve of its self-harming habits, must be the cause of intense frustration to the hell-in-a-handcart lobby. It has long been observable that the youth of today act the way the youth of two decades ago used to be told to act, when they arrived at the GP with a stomach ulcer and an anxiety disorder. They go to the gym, they have personal bests, they count their steps, they walk up stairs. They spend less on alcohol and more on coffee. Their behaviour is so different, so pronounced, that it has affected the entire cohort known as adults. The family-spending data from the Office of National Statistics reported last week that average weekly spend on alcohol, cigarettes and narcotics had fallen below £12 for the first time.

Generation X has of late cast itself as the buffer of decency between the righteous self-interest of the baby boomers and the fragile solipsism of the millennials. But the really salient development, incremental in its arrival but sudden in its obviousness, is the total rejection of hedonism, which was all we X-ers were ever good at. Alcohol consumption has been in steady decline since 2002. The 90s saw a surge, among young men in particular; between 1994 and 1999, they increased their intake by an incredible eight units a week (young women were less dramatic, starting from a lower bar, but female drinking overall increased by a third over the same period). These spikes are understood to be spurred by economic booms, although the relationship between those and a kind of cultural exhilaration must surely be symbiotic, each driving the other. To recap for the younger reader: these were the years when “binge” was a compliment; William Hague would show off about drinking 14 pints at a sitting; whole sitcoms would be built on the assumption that you could drink wine in the morning and that would be funny. It was the era of ladettes and self-parody, hangovers and fags, gleeful personal failure. All of that has been comprehensively rejected; nobody even staged a rebellion. They just thought we were silly.

There are other things happening here, sometimes in parallel, sometimes bisecting. People spend what they can afford, and other costs have gone up. Wages have stagnated, rents increased. Credit is tight and viewed with suspicion. As Reni Eddo-Lodge, a 27-year-old activist turned writer, explains to me, rather wearily: “It’s really just about money. When I was a student, I drank more heavily than I do now. I haven’t smoked since 2012. It wasn’t a puritanical thing; I just couldn’t afford to. Everybody who I was friends with when I was 18 is limiting nights out because the cash just isn’t there.” The economic circumstances since the crash have been most punishing to the young, and their behaviour has changed the fastest.

Yet their drinking attitudes reveal motivations beyond frugality: Heineken polled 5,000 21-35 year olds in five countries this year, and found that “self-awareness” and “staying in control” were two considerations behind the fact that three-quarters of millennials limited the amount they drank on the majority of nights out. The alcohol industry has been wise to this for at least a decade. Bruce Davis, an anthropologist turned, briefly, consumer-whisperer, remembers seeing this anxiety in the 00s: “It’s the one thing that’s constantly worrying drinks companies; all profits are based on volume. If you make beer, you only make money when you sell lots of it. They get really worried when they see volumes decreasing.” But as soon as the millennials came of pub age, volumes did decrease, and at that point, it was more about self-fashioning than it was about cash. “In the past, you didn’t go drinking to be individual, you went to be the same as everyone else. Volume drinking is driven by people trying to keep up with each other. Millennials’ behaviour was always much more individual. People don’t buy rounds as much. People are nomadic, they might not even stay with one group for the whole evening. It’s a much more liquid, modern social life.” But it would be a mistake to take modern as an unalloyed good; it’s partly modern because it’s atomised, insecure and precarious. “Even among working-class millennials, they’re not going to the same workplace, so they’re not drinking in the same place. The big volume push for alcohol was drinking in groups.”

Eddo-Lodge reminds us not to elide these new working patterns with a deliberated individualism. “There’s this significant uptick in the number of young people freelancing. It’s not a choice, that’s just us making the best of a bad situation.”

Swerving off the labour market and back to the pub, the industry’s response was to devise interesting spirits, drinks that would generate income even in relatively small amounts. Davis invented Monkey Shoulder whisky and Sailor Jerry’s rum, brands that “consciously sought to disassociate themselves from the generations that drank in order to get drunk”. The signature drink of this trend is craft beer, which partly through international cross-fertilisation – the Antipodeans with their more distinctive hops, the Americans with their entrepreneurialism, us with our romantic attachment to beer – has become the ultimate drink-as-self-expression, definitely-not-drunk-to-get-drunk drink. Chloe MacDonnell, 30, who works for the fashion title InStyle, lives the niche alcohol dream. “We spend a lot of money getting the best gin, or the best beer. But at the same time, I will buy a bottle of wine for a fiver in Tesco. It’s like fashion, the high and low element, designer to high street.”

There is a health element that, again, occupies that uncomfortable space between individualism and insecurity. “If you look at gym membership and gym frequency among millennials, it’s higher. You drink water and you take pills because it doesn’t make you fat,” Davis observes. (Gym-going, interestingly, may drive spending in all kinds of areas – going out to eat, clothes shopping – but it doesn’t drive people to drink.) Narcotics spending has probably gone down not because of abstinence but because drugs are cheaper and purer and altogether better, proof if any were needed that market forces do work especially well on non-essential commodities. Yet both the surge in legal highs and the spate of clubs turning into bars makes me wonder whether the majority of people just prefer not to break the law. As a footnote, notions of indulgence and masculinity have changed: it used to be signifier of something or other, something good, if you could drink 10 pints without soiling yourself. That doesn’t impress millennials so much.

MacDonnell names the defining generational difference: brunch. “Me and my friends would go out for brunch at the weekend; older colleagues think that’s just weird. Why not wait for lunch, so you can drink?” For a short time last year, I lived on a hill in the semi-suburbs of south-west London where young people would queue down the street on a Saturday morning to go to cafe/brand the Breakfast Club. I kept wanting to close-question them about it – you’re waiting in line, for an egg. Who does that? – but they all looked so fit.

Sorted for teas and brunch. Photograph: Alamy Stock Photo

Both eating out and event spending – minibreaks, day trips, experiences – have peaked this year, which illustrates that it’s not leisure that has dropped off so much as hedonism. Spending on experiences is variously characterised as a new wisdom – people realising that memories are more important to one’s identity than things – and a new self-fashioning – people deciding that mindless enjoyment didn’t add much to Project Me. Eddo-Lodge says: “Once you get out of the habit of big nights out, they’re no longer attractive. If I have a bit of disposable income, I’d rather go for a day trip. I’ve actually decided to go to Maldon.”

Sara Mahmoud, 30, is an economic analyst in the housing sector. “I’m a private renter, as a lot of young people are. When you’re renting privately, no matter what your income is, you feel that you are being made poorer by having such high rents. And you feel your life is insecure because of the instability of renting. But I know how lucky I am, because I look at household-income data all day long. What really shocked me was how many renters have no savings at all. Zero in the bank, totally hand-to-mouth. And that is really serious, because obviously, people have very limited prospects of being able to get themselves out of whatever insecure situation they’re in.”

Beyond that, it is incredibly unusual for those under 30 to think of themselves as saving to buy a house; it’s unrealistic, for anyone who doesn’t have help from their parents. “Shelter did a study that showed 50% of first-time buyers, rising to 60% in London, had help from their parents,” Mahmoud continues. “One of the things that concerns me is the concentration of wealth that that implies. But also, there is a real tension; we’re increasingly moving towards asset-based welfare. People have to rely on the value of their homes to pay for their care, while also paying for their children to get on to the housing ladder.” This colours all other decisions – where to live in the long term, when to start a family, whether to eat or put the heating on. It has a different effect on social behaviours across the income distribution. At the affluent end, there is very little point saving £50 on any single decision, since those 50 quids are not – as they would have in the 90s – ever going to add up to a deposit on a flat. At the low-waged end, there isn’t any flexibility at all, and there is more pre-loading at home, Scandinavian-style.

Yet Mahmoud, being also in a punk band, doesn’t see her generation as particularly abstemious or reserved. If anything, she thinks youth culture is rediscovering its rebellion, an antipathy to the mainstream not seen since Thatcher. “Young is really defined by social constructs over time. I wouldn’t necessarily count myself as young, but someone in the government would aim a scheme at me. Because I’m not on the property ladder, my life has only just begun. All our lives have been characterised by the financial crisis, and it is really interesting to see that feeding through to actual youth culture, how they think about the world, how they go out and enjoy themselves.”

There’s never much national mourning when unwanted, smelly, disease-causing behaviours decline; and nobody, probably, would be sorry to see the back of smoking, although I will add here that the e-cigarette technology partly driving that has left me more addicted to nicotine than I’ve ever been in my life. But large-scale restraint in the booze arena, while it may shave a few off the cirrhosis register decades hence, has implications for the present reality that we should take seriously and not cheerlead: plain lack of disposable income, for one; reordering of power between renters and rentiers, which cannot, I don’t think, be waived away with a casual, “everybody rents in Berlin”; a growing economic insecurity and intensifying personal perfectionism that can’t possibly be unrelated. All this clean living is driven by some dirty data.