Efficiently Estimating Data Efficiency for Language Model Fine-tuning

Gyung Hyun Je; Colin Raffel

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arXiv · 2512.24991

Efficiently Estimating Data Efficiency for Language Model Fine-tuning

Gyung Hyun Je·Colin Raffel

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Abstract

While large language models (LLMs) demonstrate reasonable zero-shot capability across many downstream tasks, fine-tuning is a common practice to improve their performance. However, a task's data efficiency--i.e., the number of fine-tuning examples needed to achieve a desired level of performance--is often unknown, resulting in costly cycles of incremental annotation and retraining. Indeed, we demonstrate across a curated set of 30 specialized tasks that performant LLMs may struggle zero-shot but can attain stronger performance after fine-tuning. This motivates the need for methods to predict a task's data efficiency without requiring incremental annotation. After introducing a concrete metric that quantifies a task's data efficiency, we propose using the gradient cosine similarity of low-confidence examples to predict data efficiency based on a small number of labeled samples. We validate our approach on a diverse set of tasks with varying data efficiencies, attaining 8.6% error in overall data efficiency prediction and typically eliminating hundreds of unnecessary annotations on each task. Our experiment results and implementation code are available on GitHub.

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BibTeX RIS

Gyung Hyun Je, Colin Raffel. 2025-12-31. Efficiently Estimating Data Efficiency for Language Model Fine-tuning. https://arxiv.org/abs/2512.24991

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