ForecastBench-Sim: A Simulated-World Forecasting Benchmark

2026-06-17

AI Summary

Real-world forecasting benchmarks are often constrained by outcome delays, the rarity of tail events, and the infeasibility of evaluating counterfactuals. To address these limitations, this work proposes a simulation-based forecasting benchmark built on the turn-based strategy game Freeciv. The framework generates forecasting tasks from fixed snapshots of world states and automatically evaluates predictions against subsequent simulated trajectories. It supports continuous or binary forecasts over arbitrary time horizons, as well as conditional and causal intervention queries, enabling repeatable assessment of rare or disruptive events. The authors release a complete benchmark pipeline—including a suite of forecasting questions, a scoring mechanism, and associated datasets—and demonstrate its validity through evaluations with predictive models and an anonymous human pilot study.

Abstract

Forecasting benchmarks for general-purpose AI systems usually inherit the constraints of the real world: outcomes resolve slowly, tail events are rare, and counterfactual questions are difficult to score. We introduce ForecastBench-Sim, a simulated-world forecasting benchmark built on game rollouts from Freeciv, a turn-based strategy game modelled on the Civilization series. Forecasters receive a fixed world report (a structured snapshot of the current game state) and answer questions about hidden future states; the benchmark then continues the simulation and scores forecasts. Because the world is simulated, the same setup can generate continuous or binary forecasting questions at arbitrary time horizons, paired intervention worlds for conditional or causal questions, and resolved examples of rare or disruptive outcomes. We describe the benchmark pipeline, question families, scoring protocol, and release artifacts, and report validation slices from model evaluations and an anonymized human pilot. ForecastBench-Sim is intended to complement real-world forecasting benchmarks by providing controlled, immediately resolvable tasks for studying probabilistic reasoning under dynamic world states.

Problem

• forecasting benchmark
• simulated world
• tail events
• counterfactual reasoning
• probabilistic reasoning

Innovation

• simulated-world forecasting
• probabilistic reasoning
• causal forecasting
• benchmark design
• game-based simulation