Assessing Y-Axis Influence: Bias in Multimodal Language Models on Chart-to-Table Translation

Seok Hwan Song, Azher Ahmed Efat, Wallapak Tavanapong


Abstract
Chart-to-table translation converts chart images into structured tabular data. Accurate translation is crucial for Multimodal Language Modal (MLM) to answer complex queries. We observe imbalances in the number of images across different aspects of the y-axis information in public chart datasets. Such imbalances can introduce unintended biases, causing uneven MLM performance. Previous works have not systematically examined these biases. To address this gap, we propose a new framework, FairChart2Table, for analyzing y-axis-related bias on five state-of-the-art models.Key Findings: (1) There are significant y-axis biases related to the digit length of the major tick values, the number of major ticks, the range of values, and the tick value format (e.g., abbreviation or scientific format). (2) The number of legends/entities in chart images impacts MLM performance. (3) Prompting MLM with y-axis information can significantly enhance the performance for some MLMs.
Anthology ID:
2026.findings-acl.1765
Volume:
Findings of the Association for Computational Linguistics: ACL 2026
Month:
July
Year:
2026
Address:
San Diego, California, United States
Editors:
Maria Liakata, Viviane P. Moreira, Jiajun Zhang, David Jurgens
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Findings
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Publisher:
Association for Computational Linguistics
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Pages:
35412–35430
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https://preview.aclanthology.org/ingest-acl/2026.findings-acl.1765/
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Cite (ACL):
Seok Hwan Song, Azher Ahmed Efat, and Wallapak Tavanapong. 2026. Assessing Y-Axis Influence: Bias in Multimodal Language Models on Chart-to-Table Translation. In Findings of the Association for Computational Linguistics: ACL 2026, pages 35412–35430, San Diego, California, United States. Association for Computational Linguistics.
Cite (Informal):
Assessing Y-Axis Influence: Bias in Multimodal Language Models on Chart-to-Table Translation (Song et al., Findings 2026)
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