Equity with Efficiency: An Empirical Study of Tokenizers for Multilingual Large Language Models

Kieron Seven Lee Jun Wei, Muhammad Reza Qorib, Andrew Ivan Soegeng, Hwee Tou Ng


Abstract
Multilingual large language models (LLMs) depend on subword tokenization to bridge discrete text and continuous neural representation. State-of-the-art multilingual LLMs often use Byte-level Byte-Pair Encoding (BPE) tokenizers that structurally favor high-resource languages and Latin scripts. For speakers of underrepresented languages, particularly those across Southeast Asia, this bias inflates inference costs and widens cross-lingual capability gaps. We present the first systematic comparison of equitable tokenizers on a unified benchmark spanning 11 Southeast Asian languages. Beyond tokenizer-level analysis of compression efficiency and cross-lingual equity, we assess downstream task performance through controlled 1.5B-parameter language model training using the same training data. Our results show that Parity-aware BPE lies on the Pareto frontier of the efficiency-equity trade-off, achieving strong compression parity at competitive cost. Morphology-Driven Byte Encoding delivers the best semantic reasoning performance through morphologically richer representations, albeit at a higher computational expense. Byte Latent Transformer underperforms on downstream tasks, possibly because its architectural assumptions misalign with the constraints of limited low-resource training data. Together, our findings demonstrate that cross-lingual fairness and tokenization efficiency are not fundamentally at odds, and offer practical guidance for designing equitable multilingual models.
Anthology ID:
2026.emnlp-main.1783
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
40622–40636
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1783/
DOI:
Bibkey:
Cite (ACL):
Kieron Seven Lee Jun Wei, Muhammad Reza Qorib, Andrew Ivan Soegeng, and Hwee Tou Ng. 2026. Equity with Efficiency: An Empirical Study of Tokenizers for Multilingual Large Language Models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 40622–40636, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Equity with Efficiency: An Empirical Study of Tokenizers for Multilingual Large Language Models (Wei et al., EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.1783.pdf