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LLM confidence estimates for classification suffer from sparsity, impacting evaluation

A new paper highlights significant limitations in how Large Language Models (LLMs) estimate confidence for classification tasks. Researchers found that common methods, like verbalization, result in highly sparse confidence outputs, with models often producing only a few distinct confidence values. This sparsity critically impacts evaluation metrics, such as the Area Under the Accuracy-Rejection Curve (AUARC), where different interpolation methods can drastically alter model rankings. The paper proposes a new method, "verbalization logprobs," which weights verbalized digits by token probabilities to address sparsity and improve AUARC scores without increasing inference costs. AI

IMPACT Highlights critical evaluation challenges for LLM classification confidence, potentially impacting how model performance is assessed and compared.

RANK_REASON Paper detailing evaluation pitfalls and proposing a new method for LLM confidence estimates. [lever_c_demoted from research: ic=1 ai=1.0]

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LLM confidence estimates for classification suffer from sparsity, impacting evaluation

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  1. Hugging Face Daily Papers TIER_1 English(EN) ·

    Evaluation Pitfalls and Sparsity Limitations in LLM-based Confidence Estimates for Classification

    Confidence estimation is essential when LLMs are used for classification, indicating when predictions can be trusted. However, common approaches such as verbalization produce extremely sparse outputs. For instance, Qwen3-32B verbalizes only eight unique confidence values on SST-2…