Impact factors provide one crude metric by which the "quality" of journals can be compared. When libraries are forced to make decisions about what journals they subscribe to, an impact factor is one way of judging how useful the content of a journal might be. Of course, if the library already subscribes to a journal, local usage statistics are vastly superior. So knowing a journal's impact factor is one datum a librarian might use in deciding whether to subscribe to a new journal. Of course, interest from library patrons is likely to be the overriding factor. So again, the usefulness of impact factors is limited. And they will become ever more limited as more and more of the scholarly literature becomes available under an open access license.










