In terms of by population... Ireland of course!
U2
Thin Lizzy
Cranberries
Bell X1
Sinead O'Connor
Damien Rice
The Corrs
Westlife
Rory Gallagher
Van Morrison
The Undertones
The Frames
Glen Hansard
My Bloody Valentine
The Pogues
Snow Patrol
Ash
Divine Comedy
Saw Doctors
Gemma Hayes
Something for everybody!