I tried to split the 3.1 installed base based in the new...
PS3: ~1600k
360: ~1000k
Wii: ~500k
What I did? Well the installed base in 2010 was: PS3: 750k, 360: 300k and Wii: 230k (~1.3 million).
2011 + 2012 = 1.8 million (3.1 - 1.3)
360 have less than 10% market share until 2011... 2012 it have topped ~70%... 3.1 million is not the end of the year numbers... so even with the increase I think the numbers are 1000k for 2011 and 800k for 2012.
360: 300k + 200k (2011) + 500k (2012) = 1000k
Wii: 230k + 200k (2011) + 100k (2012) = 530k
PS3: 700k + 700k (2011) + 200k (2013) = 1600k
Somebody have a better ideia to split the data???