Dark data is the inactive information companies hold but don’t use—often 60-80%...

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

Dark data is the inactive information companies hold but don’t use—often 60-80% of their stored data. This hidden data can silently eat up storage costs and even lead to $2.5 million wasted annually in inefficient management