An AI accelerator is useless without high-bandwidth memory stacked beside it, and SK hynix took 56.4% of HBM revenue in Q1 2026 — still first, but down from 63.2% across 2025 as Micron and Samsung got parts qualified with the accelerator designers. Korea ranks #1 on the Memory control basis as a direct result.
That seven-point slip is the clearest case in this atlas of a chokepoint actually loosening. HBM carries a substitutability weight of 0.95 here, near the top of the scale, because qualifying a memory vendor with an accelerator designer takes years — but years have now passed. Micron has sold out its 2026 output and HBM4 is entering volume supply from more than one vendor. A three-supplier market prices differently from a one-supplier market.
It is still a bottleneck, and the accounts say so. SK hynix closed 2025 with ₩97.15tn of revenue and ₩47.21tn of operating profit — a 49% margin — and overtook Samsung on annual profit for the first time in its history. The margin is the honest indicator here: watch it rather than the share, because it is what tells you whether the constraint is still binding.