Dark data is all the information companies collect but never use—often 60-80%...

https://victor-wiki.win/index.php/How_Do_I_Set_Up_Governance_Controls_Before_AI_Ingestion%3F

Dark data is all the information companies collect but never use—often 60-80% of their stored data. This inactive data costs businesses an average of $2.5 million a year in storage and management expenses