Repetition over Diversity: High-Signal Data Filtering for Sample-Efficient German Language Modeling

Ansar Aynetdinov, Patrick Haller, Alan Akbik


Abstract
Recent research has shown that filtering massive English web corpora into high-quality subsets significantly improves training efficiency. However, for high-resource non-English languages like German, French, or Japanese, aggressive filtering creates a strategic dilemma: should practitioners prioritize *diversity* by training once on large amounts of lightly filtered web data, or prioritize *quality* by strictly filtering for a high-quality core and repeating it over multiple epochs?

We investigate this trade-off for German by applying hierarchical quality filters to 500M web documents, comparing multi-epoch training on filtered subsets against single-pass training on a diverse corpus. Our experiments across multiple model scales and token budgets show that repeating high-quality data consistently outperforms single-pass training on larger, less filtered sets. Notably, the performance gap persists even after 7 epochs. Our findings suggest that for non-English LLMs, semantic concentration through quality filtering offers a more viable path to efficient language modeling than simply maximizing unique data volume.

We release our German language models (called **Boldt**), as well as our cleaned evaluation benchmarks to the research community. Our experiments indicate that they achieve state-of-the-art results despite training on 10-360x fewer tokens than comparable models.
Anthology ID:
2026.emnlp-main.1473
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:
33690–33710
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1473/
DOI:
Bibkey:
Cite (ACL):
Ansar Aynetdinov, Patrick Haller, and Alan Akbik. 2026. Repetition over Diversity: High-Signal Data Filtering for Sample-Efficient German Language Modeling. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 33690–33710, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Repetition over Diversity: High-Signal Data Filtering for Sample-Efficient German Language Modeling (Aynetdinov et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1473.pdf