Because the last third of 2014 was overinflated by "Tier 2" launches as a short-term price cut-assisted boost in the U.S. According to VGC's global numbers Q4 alone represented a whopping 62.4% of the XBO's sales for the year. Add in September and you have 73% of the year's sales. Typically Q4 sales of any given system represent 45-55% of the year's sales. While Q1 looks to be a bit up globally this year, we're still "only" looking at about around 1.1M for the quarter. Projecting forward through the year based on normal quaterly portions of yearly sales, we're talking about 6.5-6.6M for the year. Note that I am alotting upwards of 250k additional units due to Halo 5 (note that the effects of individual software releases on hardware sales are usually quite modest). To use an alternate calculation, my current projections for the U.S. have it at 4 million for this year; assuming the U.S. represents about 60% of global sales, that puts it at about 6.6-6.7M for the year. At most, I don't expect the XBO to sell significantly more than 7 million units this year globally. Q4's portion of the year's sales will likely be a far more normal this year. Given historical precedent I expect Sony to cut the PS4's price to $300 this year. MS will likely not take the losses incurred by a drop to $250 and they will likely only bump it down to $300 just to maintain parity. A $300 PS4 running at parity with the XBO will almost certainly nullify any prospects of the XBO having another disproportionately large Q4.

I simply don't see a scenario where the XBO does not decline YoY this year. But I do think it will grow in 2016 as I expect we'll see a cut to $250, likely concurrent with the release of a Slim model. If this does come to pass, it wouldn't be the first time a system zig-zagged in annual sales, dipping YoY one year then bouncing back the next. The 360 did it globally, the PSP did it in the U.S. & Japan, and the PS3 did it in Japan.