  With the recent appearance of LLMs in practical settings, having methods that
can effectively detect factual inconsistencies is crucial to reduce the
propagation of misinformation and improve trust in model outputs. When testing
on existing factual consistency benchmarks, we find that a few large language
models (LLMs) perform competitively on classification benchmarks for factual
inconsistency detection compared to traditional non-LLM methods. However, a
closer analysis reveals that most LLMs fail on more complex formulations of the
task and exposes issues with existing evaluation benchmarks, affecting
evaluation precision. To address this, we propose a new protocol for
inconsistency detection benchmark creation and implement it in a 10-domain
benchmark called SummEdits. This new benchmark is 20 times more cost-effective
per sample than previous benchmarks and highly reproducible, as we estimate
inter-annotator agreement at about 0.9. Most LLMs struggle on SummEdits, with
performance close to random chance. The best-performing model, GPT-4, is still
8\% below estimated human performance, highlighting the gaps in LLMs' ability
to reason about facts and detect inconsistencies when they occur.
