Halo 5 : "Industry sources support our belief that Halo 5 digital sales were much closer to half of units than the 20-25% GameStop is suggesting."

[Puppyroach]

Neither Gamestop nor these analysts know, they are only making educated guesses. MS's press releases clearly stated that it was the best selling first week EVER for a digital title in the Xbox store (I know I've said this a thousand times :)) and the previous record was held by Minecraft at 1 million. If they included Minecraft in their statement, it would mean Halo 5 was around 40% digital. We don't know for sure but MS is the best source we have.