Limits To (Machine) Learning

Fuente: arXiv
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Autores principales: Chen, Zhimin, Kelly, Bryan, Malamud, Semyon
Formato: Preprint
Publicado: 2025
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author Chen, Zhimin
Kelly, Bryan
Malamud, Semyon
author_facet Chen, Zhimin
Kelly, Bryan
Malamud, Semyon
contents Machine learning (ML) methods are highly flexible, but their ability to approximate the true data-generating process is fundamentally constrained by finite samples. We characterize a universal lower bound, the Limits-to-Learning Gap (LLG), quantifying the unavoidable discrepancy between a model's empirical fit and the population benchmark. Recovering the true population $R^2$, therefore, requires correcting observed predictive performance by this bound. Using a broad set of variables, including excess returns, yields, credit spreads, and valuation ratios, we find that the implied LLGs are large. This indicates that standard ML approaches can substantially understate true predictability in financial data. We also derive LLG-based refinements to the classic Hansen and Jagannathan (1991) bounds, analyze implications for parameter learning in general-equilibrium settings, and show that the LLG provides a natural mechanism for generating excess volatility.
format Preprint
id arxiv_https___arxiv_org_abs_2512_12735
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Limits To (Machine) Learning
Chen, Zhimin
Kelly, Bryan
Malamud, Semyon
Machine Learning
Machine learning (ML) methods are highly flexible, but their ability to approximate the true data-generating process is fundamentally constrained by finite samples. We characterize a universal lower bound, the Limits-to-Learning Gap (LLG), quantifying the unavoidable discrepancy between a model's empirical fit and the population benchmark. Recovering the true population $R^2$, therefore, requires correcting observed predictive performance by this bound. Using a broad set of variables, including excess returns, yields, credit spreads, and valuation ratios, we find that the implied LLGs are large. This indicates that standard ML approaches can substantially understate true predictability in financial data. We also derive LLG-based refinements to the classic Hansen and Jagannathan (1991) bounds, analyze implications for parameter learning in general-equilibrium settings, and show that the LLG provides a natural mechanism for generating excess volatility.
title Limits To (Machine) Learning
topic Machine Learning
url https://arxiv.org/abs/2512.12735