I've seen that stat too, roytonboy, and anyone who used to go on the terraces I the late 60s to late 70s and still goes to Premier League games now will recognise it from what they see. And if you look at videos of the period on YouTube, the sound of the singing from the terraces is of much younger voices than today. All those factors you quote mean it's changed, probably permanently.
One reflection on the terrace "activity" that used to occur - I remember reading somewhere, but can't find it now, an explanation for the rise of "hooliganism" in the late 60s being along the following lines. Until the 1960s, the terraces were filled with older adult males who wouldn't tolerate young lads running wild and would effectively keep them in check. However, with increasing prosperity not least reflected in car and TV ownership, from the early 60s onwards these older males abandoned the terraces for trips out in the car, mowing the lawn and watching Grandstand. As a result, the terraces were left to younger males' rivalry.
That's a very rough outline of a sociological explanation ... take it as you will. But it would suggest that what we saw in that period was very much of its time.
elwood,That explanation of football violence was by John Clarke,I think that it over simplifies things but maybe it was one of the reasons.
I have a book The Roots of football hooliganism an historical and sociological study ,which if you see it cheap on e bay is worth getting IMO,a bit dry but well researched and a fair bit on the skinhead period ( and much earlier).
That's a nice scarf,nice to have something that you wont see anyone else wearing.