Study of 88,927 AI chats finds LLMs overuse the em dash

In a dataset of 88,927 English-language AI chats, only 2% of user prompts contained an em dash vs 34% of LLM responses, peaking at 73% of responses in July 2025. Em dash use in US-published books has declined since peaking in 1979, and em dash search interest grew 245% year-over-year.