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

https://www.protopage.com/faith_morris97#Bookmarks

Dark data is the information your company collects but never uses—think 60-80% of your stored data lying dormant. It’s more than just digital clutter; keeping it can cost you around $2.5 million a year in storage, security risks, and lost opportunities