Sector-Specific Financial Sentiment Lexicons for Portuguese: Evidence from Brazilian Stock News

Antônio Artur de Souza, Mateus Binda, Adriana S. Pagano


Abstract
This paper investigates whether sector-specific financial sentiment lexicons improve the analysis of Brazilian stock-market news in Portuguese. We use 19,460 news items about 38 firms in the financial, electric, and manufacturing sectors, published between 2020 and 2025. Starting from OpLexicon, we build sector-specific lexicons through unsupervised expansion based on PMI and conditional word-polarity association. The lexicons are evaluated by lexical heterogeneity and through LSTM price forecasting. Results show sectoral variation and moderate classification performance, but limited predictive gains. Sentiment improves forecasting only in manufacturing, while other sectors do not benefit from its inclusion. The findings indicate that sector-specific lexicons are useful resources, although their predictive value are context dependent.
Anthology ID:
2026.stil-1.35
Volume:
Proceedings of the 17th Brazilian Symposium in Information and Human Language Technology
Month:
October
Year:
2026
Address:
Cuiabá, Mato Grosso, Brazil
Editors:
Bryan Khelven da Silva Barbosa, Aline Paes, Ariani Di Felippo
Venue:
STIL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
433–440
Language:
URL:
https://aclanthology.org/2026.stil-1.35/
DOI:
10.5753/stil.2026.25274
Bibkey:
Cite (ACL):
Antônio Artur de Souza, Mateus Binda, and Adriana S. Pagano. 2026. Sector-Specific Financial Sentiment Lexicons for Portuguese: Evidence from Brazilian Stock News. In Proceedings of the 17th Brazilian Symposium in Information and Human Language Technology, pages 433–440, Cuiabá, Mato Grosso, Brazil. Association for Computational Linguistics.
Cite (Informal):
Sector-Specific Financial Sentiment Lexicons for Portuguese: Evidence from Brazilian Stock News (de Souza et al., STIL 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.stil-1.35.pdf