I read something about this the other day
metro.co.uk/2017/09/27/millennials-think-getting-drunk-is-pathetic-and-embarrassing-6958560/
I'm "late millenial", I presume this survey is more from those at the other end. Being early 30s I have friends on both sides of the bordering generations; I must admit, if I scroll down my Facebook newsfeed on an average weekend, I see more photos of my 37-45 year old friends getting hammered than I do of friends in their 20s. Drunken selfies, videos of them being raucous, pictures pretending to grope each other, blurry pics - it does come across a bit cringey at times.
I think that millennials get a hard time and called narcissists (and sometimes that's deserved), but I do think there's a generation in the "born in the 70s, with kids under 13, middle class" category whose decorum on social media could give millennials a run for their money at times
I realise that's a sweeping statement but that's based on my own personal experience so I hope it doesn't cause offence.