A Nontrivial Upper Bound on the Out-of-Sample $R^2$ in Return Forecasting

Fuente: arXiv
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Auteur principal: Zhang, Cheng
Format: Preprint
Publié: 2026
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author Zhang, Cheng
author_facet Zhang, Cheng
contents This study establishes a nontrivial upper bound on the out-of-sample $R^2$ ($R^2_{\text{OOS}}$) in return forecasting. In particular, we define a coin-flip oracle model that, under the same directional accuracy, theoretically outperforms practical models in terms of MSE. The $R^2_{\text{OOS}}$ of the oracle model, whose analytical expression is a quadratic function of directional accuracy, can therefore serve as a tractable upper bound on the actual $R^2_{\text{OOS}}$. Empirical analyses across multiple forecasting scenarios reveal that the $R^2_{\text{OOS}}$ values of common predictive models are fundamentally bounded by this quadratic function.
format Preprint
id arxiv_https___arxiv_org_abs_2602_07841
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A Nontrivial Upper Bound on the Out-of-Sample $R^2$ in Return Forecasting
Zhang, Cheng
Econometrics
Statistical Finance
Applications
This study establishes a nontrivial upper bound on the out-of-sample $R^2$ ($R^2_{\text{OOS}}$) in return forecasting. In particular, we define a coin-flip oracle model that, under the same directional accuracy, theoretically outperforms practical models in terms of MSE. The $R^2_{\text{OOS}}$ of the oracle model, whose analytical expression is a quadratic function of directional accuracy, can therefore serve as a tractable upper bound on the actual $R^2_{\text{OOS}}$. Empirical analyses across multiple forecasting scenarios reveal that the $R^2_{\text{OOS}}$ values of common predictive models are fundamentally bounded by this quadratic function.
title A Nontrivial Upper Bound on the Out-of-Sample $R^2$ in Return Forecasting
topic Econometrics
Statistical Finance
Applications
url https://arxiv.org/abs/2602.07841