Global Merger-Arbitrage Forecasting with Language Models
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Abstract (arXiv)
We present a language-model forecasting system for merger arbitrage, a specialized high-stakes financial setting in which the task is to predict the outcome of announced M&A deals. Unlike prior work on judgmental forecasting with LLMs, which has focused on broad mixed-topic benchmarks and short context such as news snippets, we study a setting that requires long-context reasoning over hundreds of pages of technical documents. Our system combines expert-guided context engineering with finetuning on hindsight-guided reasoning traces derived from historical deals. Given an announced deal, it outputs a probability distribution over three mutually exclusive outcomes: closing at announced terms, a higher bid, or deal termination. On an out-of-sample set of more than 400 large deals spanning 42 countries, our finetuned system achieves the best performance of any method we evaluate, reducing class-balanced Brier score to 0.151. This is 24% below calibrated market-implied probabilities, 19% below XGBoost, and 25-42% below frontier language models. These results, together with ablation studies, show that LLM-based forecasting can succeed in specialized, long-context financial workflows, with hindsight-based supervision and expert-designed context playing a critical role.
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References · 17
- 2022ReAct: Synergizing Reasoning and Acting in Language Modelscited by 8,355
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- 2024Approaching Human-Level Forecasting with Language Modelscited by 102
- 2024Wisdom of the Silicon Crowd: LLM Ensemble Prediction Capabilities Rival Human Crowd Accuracycited by 66
- 2024Consistency Checks for Language Model Forecasterscited by 27
- 2025Pitfalls in Evaluating Language Model Forecasterscited by 23
- 2024AI-Augmented Predictions: LLM Assistants Improve Human Forecasting Accuracycited by 21
- 2025Outcome-based Reinforcement Learning to Predict the Futurecited by 21
- 2025Bench to the Future: A Pastcasting Benchmark for Forecasting Agentscited by 20
- 2024Are LLMs Prescient? A Continuous Evaluation using Daily News as the Oraclecited by 19
5 more
- 2024Can Language Models Use Forecasting Strategies?cited by 13
- 2024Greenback Bears and Fiscal Hawks: Finance is a Jungle and Text Embeddings Must Adaptcited by 12
- 2025AIA Forecaster: Technical Reportcited by 9
- 2024Reasoning and Tools for Human-Level Forecastingcited by 7
- 2021Alignment Problems With Current Forecasting Platformscited by 2
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