Real life facepalm here
Golf GTI (200bhp) on an 06 reg was just under £2,000 on Bell for me in September before my 21st birthday.
The same car, all other factors besides age constant, is now just a shade over £800 to insure.
The Mini Cooper I took insurance out on before my 21st birthday was around £700. I can now, 2 months later, insure a brand new 59 plate Cooper S for about £50 more, the quote back then was around £1,500.
So clearly from this data, statistics show that there is indeed quite a significant difference in risk between a 20 year old male driver and a 21 year old male driver. The prices do obviously not reflect the change of risk over 2 months but over the entire period as a 20 year old and a 21 year old as a whole.
(Just realised these quotes are for the 10 month policy)