Determining total sales numbers for games is harder than ever these days, as Microsoft tends to get a large percentage of their sales from digital purchases, while sales data typically only track retail sales. With Microsoft having recently reported that Xbox Live monthly active users have grown to an impressive 39 million, we may expect a record high percentage of digital sales for Halo 5. 40 % digital sales is a reasonable estimate, especially considering the online focus of the Xbox One Games and entertainment system. 150000 of Halo 5 in retail thus correspond to 250000 total sales. For Halo 4, we may estimate a more modest percentage of digital sales of 15 %, as it was released back in 2012, when Internet penetration in the UK was lower. 336000 Halo 4 copies sold in retail thus corresponds to roughly 400000 copies sold total. With those numbers in hand, we can perform the simple calculation 250000/400000 = 0.625, which indicates a decline in launch week sales of 37.5 % game over game.
Of course, if the current game-to-game decreases continue, the Halo franchise would eventually die out in the UK. However, that process would take quite a while. The figure below shows just how long, projecting out how sales of future installments would look if the Halo games launch week sales continued to decrease by about 37.5 percent per installment.
It's important to note that game sales patterns decidedly do
not work in this way, and it's a bit ridiculous to expect sales for each consecutive installment to continue decreasing in this kind of parabolic curve. Still, it's interesting to see that based on current trends, the Halo series wouldnt be reaching levels at which it should be considered dead until that unlucky number 13 in the series. That is very far into the future, and by that point, Microsoft will have sold tens of millions of Halo games, giving them nice profits.
The takeaway from this hypothetical is clear: Halo sales need to worsen at a significantly faster rate for Microsoft to run any risk of their crown jewel franchise dying any time soon.
Sony-GAF may concern troll all day long that the series is dying, but for anyone else, it looks like Halo has a long healthy life ahead.