How much of the collection is used?
This visualization is taking an optimistic look at the number of books that go unused each year. Let’s make some radical assumptions: The only items people checkout are books, and each book is a unique title and is only checked out once/year. This chart shows the increasing percentage of books that would be left untouched on the shelves each year. This figure peaks in 2010 at nearly 83%. The conclusion here is that it is a fairly conservative estimate to claim that 83% of all books on the shelves of academic libraries will not leave the library on a given year.
Some things to consider: The number of books collected by the Department of Educational Statics includes items that never leave the library: Government docs, references materials, bound serials. Realistically it is very unlikely that each book checked out is a unique title. Taking both of these into account I’d say that 83% is probably lower than the real percent of unused books each year.
The really interesting question is how many of these books have never been checked out? I don’t have the data for this, but I would be willing to bet as high as 70% due to the likely high number of books that are repeatedly checked out each year.