FEVER: a Large-scale Dataset for Fact Extraction and VERification
James ThorneAndreas VlachosChristos ChristodoulopoulosArpit Mittal
Introduces FEVER, a benchmark dataset of over 185,000 claims that challenges automated fact-checking systems to jointly verify assertions and retrieve supporting textual evidence from Wikipedia.
The rapid growth of online text and digital information sharing has created an urgent need for automated fact-checking systems across journalism, science, and consumer applications. Existing automated verification benchmarks have historically been constrained to a few hundred claims or provided pre-selected evidence passages, failing to reflect the real-world challenge where systems must actively retrieve and assemble justification from large, open text corpora.
The article introduces and evaluates FEVER (Fact Extraction and VERification), a new large-scale publicly available benchmark designed to evaluate automated systems on extracting supporting or refuting evidence from Wikipedia and classifying claim truthfulness. The authors developed a standardized, multi-step pipeline combining document retrieval, sentence selection, and textual entailment to measure baseline machine performance against human-annotated standards.
The dataset comprises 185,445 claims generated and manually verified against introductory sections of approximately 50,000 Wikipedia pages by a trained 50-member annotation team. Claims were classified into three categories—supported, refuted, or not enough info—with precise sentence-level evidence recorded for the supported and refuted categories. The evaluation pipeline coupled statistical term-matching retrieval tools with a neural decomposable attention entailment model to predict veracity and return justifying sentences.
The analysis yielded several key findings regarding task feasibility and system capabilities. First, the baseline pipeline achieved 31.87% accuracy on the test set when requiring the correct supporting evidence alongside the classification, but achieved 50.91% accuracy when evidence requirements were ignored. Second, component-level oracle evaluations and manual error analyses revealed that information retrieval—specifically selecting the exact justification sentences—is the primary bottleneck, accounting for 58.27% of system failures. Third, multi-hop reasoning is essential: 16.82% of claims require combining multiple sentences as evidence, and 12.15% require evidence spanning multiple distinct documents. Finally, data ablation demonstrated that model accuracy steadily scales with increased training volume, confirming that the dataset is sufficiently large to train complex modern machine learning architectures.
These results indicate that automated claim verification is feasible but remains constrained by retrieval precision. For organizational decision-makers and technology leaders, deploying verification systems without requiring verifiable evidence links poses a substantial risk of producing ungrounded decisions. Unlike traditional natural language inference tasks that assume the reference text is already provided, practical automated verification requires robust end-to-end evidence retrieval to ensure reliability, explainability, and compliance.
To drive progress, researchers and practitioners should prioritize developing advanced retrieval architectures capable of multi-hop sentence selection across multiple documents, rather than focusing solely on classification classifiers. Future initiatives could explore combining automated question generation, neural theorem proving, and reading comprehension models. Before operational deployment in high-stakes domains, automated verification systems should incorporate crowd-sourced human validation to handle ambiguous phrasing, missing evidence paths, and conflicting source information.
The findings are bounded by the dataset reliance on Wikipedia introductory sections and the observation that human annotators did not exhaustively capture every alternate valid piece of evidence, achieving 72.36% recall against unconstrained expert annotators. Nevertheless, strong inter-annotator agreement (a Fleiss kappa score of 0.6841) and high baseline annotation quality (91.2% author-validated precision) provide high confidence that the benchmark offers an effective, rigorous testbed for developing the next generation of fact-checking technologies.
- Paper: Natural Questions: A Benchmark for Question Answering Research, Tom Kwiatkowski et al. (2019). Natural Questions establishes the methodology of extracting questions and evidence directly from Wikipedia logs, serving as a foundational benchmark that FEVER extends to fact verification.
- Paper: Can a Suit of Armor Conduct Electricity? A New Dataset for Open Book Question Answering, Todor Mihaylov et al. (2018). OpenBookQA demonstrates how to construct datasets requiring multi-step fact combination, providing essential context for the evidence-retrieval challenges explored in FEVER.
- Paper: Think you have Solved Question Answering? Try ARC, the AI2 Reasoning Challenge, Peter Clark et al. (2018). ARC highlights the limitations of surface-level text matching in reasoning benchmarks, directly motivating the rigorous evidence extraction and verification tasks introduced in FEVER.
- Paper: BoolQ: Exploring the Surprising Difficulty of Natural Yes/No Questions, Christopher Clark et al. (2019). BoolQ investigates the complex inference demands of natural user queries, establishing evaluation patterns that inform the claim verification challenges in FEVER.
- Paper: HotpotQA: A Dataset for Diverse, Explainable Multi-hop Question Answering, Zhilin Yang et al. (2018). HotpotQA builds directly upon the multi-hop evidence extraction paradigm established by FEVER to test complex reasoning across multiple Wikipedia documents.
- Paper: BEIR: A Heterogenous Benchmark for Zero-shot Evaluation of Information Retrieval Models, Nandan Thakur et al. (2021). BEIR adopts fact-checking datasets like FEVER into its heterogeneous retrieval benchmark to evaluate how well dense and lexical models generalize in zero-shot settings.
- Paper: Text Embeddings by Weakly-Supervised Contrastive Pre-training, Liang Wang et al. (2022). E5 extends retrieval methodologies by applying weakly supervised contrastive pre-training to improve performance on text verification and search tasks pioneered by FEVER.
- Paper: Precise Zero-Shot Dense Retrieval without Relevance Labels, Luyu Gao et al. (2023). HyDE leverages zero-shot dense retrieval techniques to improve upon the baseline evidence-finding pipelines initially evaluated in datasets like FEVER.
