If you are good with math, help me with this!!!

[SnesTea]

Okay here's the thing, I am trying to figure out the market shares for previous console generations and I can't figure out how to do it! Does anyone know an equation that will help me with this? I am trying to figure out what percent of the market each system had. HELP!!!!

Or, if you want to do it yourself and tell me, that's cool, I guess. Here are the figures (rounded up to the nearest whole number)

PS2 - 140 million

Xbox - 24 million

GameCube - 22 million

Dreamcast - 11 million

 

Thanks in advance!