37% attach rate for MK8 on Switch. *Not including digital downloads



Also have to consider that Mario Karts tend to not launch in the same year as the system's debut, and that MK8 on Switch is more or less a port, plus a few new features, so millions in Japan already own that game on Wii U.



Switch is clearly also still heavily supply-constrained, and I think sales for both the system and the game would've been quite a bit higher had everyone who wanted a Switch been able to get one. There's likely a lot of people who want Mario Kart but can't play it because they can't find a system.



Nintendo is cranking right now!