I had a little spare time so here's the ranking based on dollars spent per capita :
1-Japan 23.68 $
2-UK 20.41 $
3-Australia 18.35 $
4-Germany 16.97 $
5-France 14.51 $
6-US 14.065 $
7-Canada 12 $
8-South Korea 4.20 $
9-Italy 3.97 $

10-Brazil 1.13 $
If an american spent as much as a japanese, the market would amount to 7.525 billion dollars. If every country and population on earth had the same prices and behaviours as Japan, the music indistry would be worth 169.4 billion dollars.