From Index to Equity: Pre-Training Transformers for Stock Return Prediction

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Hauptverfasser: Coolsaet, Marie Soehl, Gallardo, Roberto, Gao, Zhen
Format: Preprint
Veröffentlicht: 2026
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author Coolsaet, Marie Soehl
Gallardo, Roberto
Gao, Zhen
author_facet Coolsaet, Marie Soehl
Gallardo, Roberto
Gao, Zhen
contents This research aims to leverage machine learning to improve stock price prediction and support informed investment decisions related to buying, selling, and holding assets. Specifically, this work investigates transformer-based models for stock prediction and examines the impact of pre-training strategies on forecasting performance. A transformer model was first pre-trained on the Toronto Stock Exchange Index (TSX) to predict intra-day return direction and subsequently fine-tuned on individual TSX stocks. The model was further adapted for return-value regression tasks. Performance was benchmarked against Long Short-Term Memory (LSTM) and XGBoost models. Pre-training on the market index improved the binary cross-entropy loss for individual stock prediction from 0.69 to 0.64. The fine-tuned transformer regression model achieved lower mean squared error than the benchmark models, although the ensemble and XGBoost models achieved higher average daily returns. In addition, a practical application was developed to deliver real-time stock predictions for trading support. Future work will focus on increasing transformer model capacity, incorporating broader global technical indicators, and filtering out stocks with low predictability.
format Preprint
id arxiv_https___arxiv_org_abs_2605_23962
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle From Index to Equity: Pre-Training Transformers for Stock Return Prediction
Coolsaet, Marie Soehl
Gallardo, Roberto
Gao, Zhen
Statistical Finance
Machine Learning
This research aims to leverage machine learning to improve stock price prediction and support informed investment decisions related to buying, selling, and holding assets. Specifically, this work investigates transformer-based models for stock prediction and examines the impact of pre-training strategies on forecasting performance. A transformer model was first pre-trained on the Toronto Stock Exchange Index (TSX) to predict intra-day return direction and subsequently fine-tuned on individual TSX stocks. The model was further adapted for return-value regression tasks. Performance was benchmarked against Long Short-Term Memory (LSTM) and XGBoost models. Pre-training on the market index improved the binary cross-entropy loss for individual stock prediction from 0.69 to 0.64. The fine-tuned transformer regression model achieved lower mean squared error than the benchmark models, although the ensemble and XGBoost models achieved higher average daily returns. In addition, a practical application was developed to deliver real-time stock predictions for trading support. Future work will focus on increasing transformer model capacity, incorporating broader global technical indicators, and filtering out stocks with low predictability.
title From Index to Equity: Pre-Training Transformers for Stock Return Prediction
topic Statistical Finance
Machine Learning
url https://arxiv.org/abs/2605.23962