Evaluating the Impact of Text Quality in Web-Crawled Corpora for LLM Training
Introduction to Corpus Quality and LLM Performance
The deployment of web-crawled corpora in training LLMs (LMs) represents a cornerstone of recent advancements in NLP. These corpora, often vast and unstructured, raise critical questions about the role of data quality on LM performance. In response to this, an insightful paper spans an extensive evaluation across four populous web-crawled corpora, namely CC100, MaCoCu, mC4, and OSCAR, focusing on their qualitative aspects and the subsequent effects on training LLMs across eleven lower-resourced European languages.
Manual Evaluation: A Dive into Data Quality
The researchers embarked on a detailed examination of the aforementioned corpora through a dual-phase evaluation. The manual evaluation entailed professional linguists scrutinizing data quality based on a multi-tiered annotation scheme. This phase revealed significant qualitative differences among the corpora. MaCoCu and OSCAR emerged as front-runners in quality, exhibiting a higher prevalence of publishable and coherent running text, while mC4 exhibited notable deficiencies, especially in representing the Maltese language, where a large fraction of data was inaccurately labeled or lacked coherence.
Automatic Evaluation: Exploring LLM Performance
The paper advanced to an automatic evaluation by training LLMs on segments of these corpora for a subset of five languages. Surprisingly, despite the quality disparities highlighted during the manual evaluation, CC100 led in achieving superior performance in downstream tasks, suggesting a complex relationship between raw data quality and LM efficacy. This phase interestingly showcased that the quality of data, as judged through human evaluation, does not straightforwardly translate to expected outcomes in LM training, underscoring the resilience of LMs to diverse data quality.
Implications and Future Directions
The findings prompt a reevaluation of the criteria for curating training corpora for LMs, especially under the premise that sheer data volume does not equate to quality. This research unequivocally shifts the discourse towards understanding the nuanced dynamics between data quality and LM performance, challenging the prevailing notion that higher quality datasets invariably lead to superior model performance.
This work also sets the stage for future explorations into the mechanisms through which LMs can adapt to or leverage variances in data quality. It opens up pathways for developing more robust models that can efficiently handle the intricacies presented by web-crawled corpora, particularly for lower-resourced languages that often suffer from data paucity and quality issues.
In conclusion, this paper contributes a critical perspective to the ongoing dialogue on the optimization of data sources for LM training, providing evidence-based insights that question established assumptions and pave the way for refining data curation practices and model training methodologies in the evolving landscape of natural language processing.