90% of papers that have been published in academic journals are never cited. Indeed, as many as 50% of papers are never read by anyone other than their authors, referees and journal editors.

 --- Lokman I Meho in The rise and rise of citation analysis (2007) Phys. World 20 (1) 32, 

Abstract

It is a sobering fact that some 90% of papers that have been published in academic journals are never cited. Indeed, as many as 50% of papers are never read by anyone other than their authors, referees and journal editors. We know this thanks to citation analysis, a branch of information science in which researchers study the way articles in a scholarly field are accessed and referenced by others.

Via Marc Abrahams in New Scientist's Feedback column, 20 March 2024, which also notes

The second question got a good going-over by Martin Paul Eve at Birkbeck, University of London. His new study (which also hasn’t yet disappeared) is called “Digital scholarly journals are poorly preserved: A study of 7 million articles”. The study did an “appraisal” of 7,438,037 scholarly citations that have unique identification codes called DOIs. Well, the study attempted to do an appraisal. Eve reports that 2,056,492 (27.64 per cent) of those items appear to be missing.