It's not hard to see how mistakes could happen. Shelving books is a labor-intensive activity that in the best of times can take up to 48 hours. But at the end of each semester, Jackson said the library gets hit with 40,000-50,000 returned books to shelve in not much more than a week. The library shifts a large amount of manpower to the shelving effort at the end of the semester, but it takes at least three weeks and generally more to clear out this backlog. Faced with a mountain of books to shelve in a short period of time, errors occur.
Human beings make mistakes.
We just have to make the effort to find them and correct them. But other factors complicate things. As important as shelf reading is, there is nothing exciting or easy about it, Jackson said. Walking around the fourth floor stacks, Jackson points out the variety of books and the ways the Dewey number is placed on the book. The numbers can go for four, five lines, particularly on the thin books, and sometimes adjacent volumes can have very similar numbers, making mistakes more likely.