Polymarket Calibration Benchmark, 2026 Q3 (OVERROUND)

Market-level calibration and Brier scores for Polymarket, computed from public on-chain data over a fixed twelve-month window (markets resolved 2025-07-01 through 2026-06-30, excluding voided, disputed, and short-duration Up/Down markets). Four CSV tables: horizon decay over a constant 21,992-market universe, per-horizon full universes, calibration curves by price decile at 24 hours and 30 days, and accuracy by category at 24 hours. Three republishable chart PNGs render the same tables. Methodology, limitations, and the reconciliation of conflicting public accuracy figures: https://www.overround.pro/benchmarks/polymarket-calibration-2026-q3 Produced by OVERROUND (overround.pro), an independent analytics project on publicly available prediction-market data. Immutable edition; a new quarter publishes a new edition.