Collection development entails the art of ensuring that all pieces of the library's information collection are up-to-date, accurate, and sufficient for the audience of the library. Collection development involves a continual analysis and evaluation of what the library already has (this is usually done by checking to see how much of each subject matter and genre you already have), what is needed, and what is out-of-date and needs to be weeded out, or gotten rid of. This is a complicated and ever changing task which does not ever really end. A librarian should always be perusing their shelves and data stores to check for wear and tear of items, books or other materials that are visibly old, and keeping an open ear to what visitors are looking for that you cannot currently offer. Doing this will help you ensure that when you order new materials, they are what you really need, and make sure you have an efficient, not just large, media and book collection.