Barozi on 03 February 2013
Better write him a PM...
He started showing XBLA sales a long time ago on VGC. He kept track of leaderboards, looked at mygamercard.net game ownerships and could thus get valuable informations. Furthermore quite some XBLA developers shared some sales informations so he could connect his estimations with real sales data.
I guess he could have also connections with some PSN/Steam/Android/iOS/XBLA developers who share sales informations of their games etc.
Also Sony and Microsoft release best selling PSN/XBLA lists (without numbers) which also helps.
