Financial Evidence Crowding: Diagnosing and Mitigating Constraint-Induced Displacement in Retrieval-Augmented Generation

Abstract

Retrieval-augmented generation (RAG) retrieves candidate evidence and sends only a limited top-ranked subset, the top-k context, to a generator. In financial question answering, passages can match a query's topic while conflicting with its period, segment, metric scope, or table scope. We study the resulting set-level ordering failure, which we call financial evidence crowding. FinDeCrowd-Stress isolates this failure through matched compatible and incompatible candidate pools while fixing the query, relevant evidence, ranking model, candidate count, and retrieval budget. On a FinDER test split containing companies unseen during training, incompatible pools reduce top-10 evidence inclusion (Recall@10) by 0.147 relative to equally difficult compatible pools. This gap shows that conflicting candidates consume limited context slots and displace answer-supporting evidence. We then introduce FinDeCrowd-RAG, a learned score correction that combines a fixed relevance score with typed compatibility and local lexical competition. A query-level identity gate applies the correction only when it predicts a better order; otherwise, it preserves the original ranking. On identical controlled candidates, FinDeCrowd-RAG raises top-10 evidence inclusion from 0.757 to 0.902 by recovering evidence already present in the candidate set. On a FinDER index built without query-specific candidate insertion, gated reranking raises this inclusion rate from 0.420 to 0.492, while top-100 retrieval coverage remains 0.743 by design. With a fixed generator, the same ordering change improves answer accuracy and citation recall on FinanceBench and FinQA. These results identify constraint-induced displacement as a measurable RAG evaluation target and show that identity-gated reranking can recover evidence already covered by first-stage retrieval.