Dark data is all the information companies collect but never use—think emails,...

https://www.apu-bookmarks.win/dark-data-is-the-information-companies-collect-but-never-use-often-making-up-2

Dark data is all the information companies collect but never use—think emails, old files, or system logs. It can make up 60-80% of stored data, costing businesses up to $2.5 million a year in storage and management fees