Dark data is all the information companies collect but never use—often making...

https://yenkee-wiki.win/index.php/Why_Does_Dark_Data_Make_Enterprise_Search_Results_Useless%3F

Dark data is all the information companies collect but never use—often making up 60-80% of stored data. It matters because holding onto this inactive data wastes money and space, sometimes costing businesses over $2.5 million a year