PS4 Sells 5.9 Million Units Worldwide During 2017 Holiday Season, >73.6 Million Sold Through

[VideoGameAccountant]

CGI-Quality said:
20.2m for 2017, then. Can't say what year will be the peak, but I can see them selling more than 20 million units this year.

I think the PS4 definitely benefited from the improvements in the economy. If 2017's economy was like 2016's, I'd expect it would have peaked in the 3rd year. I should note this has definitely helped the Switch and the XBox One X as well. There is also the fact that some of these sales are PS4 Pro sales, which means you have Sony selling to customers who already own a PS4 (i.e. More PS4s in the wild but fewer owners). I see it declining in 2018 as it reaches the end of its lifecycle.