I've found it! For years I've wondered how much a vast majority was. 51%? 99%? But this, found in the Mail, has, after all my lonely ponderings, given me the answer:
The Premier League poppy group gained three more members on Tuesday when Fulham, Aston Villa and Portsmouth joined the vast majority of top-flight clubs who are now embroidering a poppy on their matchday shirts to mark Remembrance Sunday.
This leaves just five clubs who won’t be displaying a poppy: Manchester United, Liverpool, Stoke, Blackburn and Bolton.
Twenty teams in the Premier League, so it's 75%! Precisely three quarters! The great question is solved.
Once, when I was young and foolish, I thought that it was just a meaningless phrase for journalists who didn't know any figures. Then I discovered how much the Economist uses the words - 560 times on their website - and so I knew, knew beyond doubt, that there must be a precise value to vastness.
That or the Mail is better with numbers and raw information than the Economist is.
A typical day in The Economist's newsroom
Possible correction: I've just realised that before Fulham, Aston Villa and Portsmouth joined, there would only have been twelve out of twenty. So it's 60% unless the vast majority has only been achieved now that the other clubs have joined.