ZhugeEX on 28 January 2016
During their post earnings conference call EA said that the PS4 and XB1 install base (sell through) had reached approximately 55 million as of December 31st 2015.
Please note that this is an estimate from EA and therefore is based on their internal research + IDG numbers or whatever market research companies they subscribe to.
We know that Sony have sold 35.9 million as of January 2nd so we can estimate that the Xbox One is somewhere around ~19 million. Give or take.
