We still lack a real y-axis for AI capability: benchmark scores, Elo, ECI, METR all flawed

sebkrier · x · 2026-11-10

sebkrier argues that assessing AI trajectories requires a y-axis where +1 always means the same degree of improvement — and none of our metrics provide it. Researchers know this, but the implication gets lost in discourse.

The attached breakdown covers the flaws of each measure: benchmark scores are nonlinear and uninterpretable as increments; Elo gives real winning odds but doesn't translate beyond beating others; Epoch's Capabilities Index is IQ-like, with intervals dictated by modelling assumptions, and since benchmarks are endogenous to the models, the 2024 acceleration in ECI and Time Horizon may be a shared measurement artefact rather than mutual corroboration; log-loss is nonlinear like reaction time; and METR's time horizon (10^(k×score)) is essentially human psychometrics — under linear time horizon, Opus 4.5→4.6 would outweigh dawn-of-time→Opus 4.5.

Original post →

More from AGI Musings

AGI Musings channel →