Dark data is the information your company collects but never uses—often 60-80%...

https://domgodwinson38.gumroad.com/p/why-do-ai-answers-hallucinate-when-there-are-duplicate-documents

Dark data is the information your company collects but never uses—often 60-80% of all stored data. This unused data takes up space, costs money to manage, and can hide security risks