Dark data is all the info your company collects but never uses—sometimes 60 to...

https://charlie-wiki.win/index.php/What_is_a_Global_Metadatabase_and_Why_Would_I_Want_One%3F

Dark data is all the info your company collects but never uses—sometimes 60 to 80% of it sits inactive. It matters because storing and managing this unused data can cost millions each year, often $2.5 million or more