How Grounded is Wikipedia? A Study on Structured Evidential Support and Retrieval

Wikipedia is a critical resource for modern NLP, serving as a rich repository of up-to-date and citation-backed information on a wide variety of subjects.The reliability of Wikipediaits groundedness in its cited sources-is vital to this purpose.This work analyzes both how grounded Wikipedia is in this sense and how effectively fine-grained grounding evidence can be retrieved.To this end, we introduce PEOPLEPROFILES 1 -a large-scale, multi-level dataset of claim support annotations on biographical Wikipedia articles.We show that: (1) ∼22% of claims in Wikipedia lead sections are unsupported by the article body; (2) ∼30% of claims in the article body are unsupported by their (public) sources; and (3) real-world Wikipedia citation practices often differ from documented standards.Finally, we show that complex evidence retrieval remains a challenge, even for recent reasoning rerankers.