I maintain the adult non-fiction 500s in my library. I normally let an Intern have their way with my collection, so it gets a concentrated weed at least annually. I also believe that collection management should be on-going, so I am constantly picking at the 500s. In that regard, there's rarely something truly awful in the 500s. There are some lingering items that haven't circulated well, or that are on schedule to be weeded the following year, but I deal with items in bad condition and unnecessary duplicates on an ongoing basis.
Here's how it works for the annual Intern weeding project:
1. What hasn't circulated in three years? Weed 'em. I am fortunate to have a budget, space, and patron demand that can keep up with a three-year cycle. Of course, the Intern and I still look closely at what is showing up in this report. We don't just weed everything that hasn't circulated in three years. Some things are left alone for another year or two, depending on what they are and their purpose.
2. What is older than ten years? Depending on the subject area and its dependency on currency, weed 'em. For example, many math books, plant books, and animal books are ok up to (and even beyond) ten years. There are also some classics (for example, Stephen Hawking's older books) that are going to be kept for a while yet too.
3. What is older than five years? See #2. These are more timely categories. Pluto kicked out of the planet club? Weed 'em.
Now it's time for some metrics! We've removed the dead weight based on the above criteria, and a new shelf list is run for the 500s. Using Excel, it is sorted by publication date (or "date created" if you're using the ILS I'm using, since that's all we have to work with. Seriously.)
Currently, here are the stats on my 500s. Keep in mind that "date created" is not the same as "publication date." 1994 is when the library was first automated, so there are no records older than 1994. The actual publication date of those 38 items (see chart below) could be much older. I have to look at each of those 38 item records individually to find out their publication dates. We could spend tens of thousands of dollars for an ILS reporting module that would give us more data...but we haven't. Our ILS manager might be able to dig deeper, but at my level of permissions, I can't. It's ok; 38 items is still manageable. This is why collection management should be ongoing; so 38 doesn't turn into 538. Also, most of the records created in each year are for items published in that year.
The chart below shows the median age, the average age, and what percent of the collection fall within various ages. 38% are five years old or newer, 76% are nine years old or newer (this includes the 38% that are five years old or newer, but it is easy enough to see that 38% are between 6-9 years old) , and 24% are ten years old or older.
It is possible that the budget for 500s was larger in certain years, or that a higher number of materials were published in certain years, or that more materials with lasting value were published in certain years. I'll do a separate post about metrics for specific Dewey call numbers. Remember that we're looking at the 500s as a whole, lumping time-sensitive subjects in with less-so subjects. We can do these same calculations for just math books, just physics books, etc. and see how the pub dates break down.
I have not updated this chart for 2014 yet because we put new non-fiction into a collection called "Adult New Non-Fiction." The group metrics gathered on all new books in the 500s fall under "Adult New Non-Fiction" - along with all other new books in other Dewey ranges. It will be about June before 2014 books in the 500s start collecting metrics in the actual category of "Adult Non-Fiction 500s." The item metrics are still valid for those items - how many times each of them has circulated, when their records were created, etc. but the group metrics for those items don't begin to gather until they are taken out of "Adult New Non-Fiction" and into "Adult Non-Fiction 500s." Unfortunately, you can't pull metrics on just new 500s out of "Adult New Non-Fiction."
Stay tuned for another post on the next step in using collection metrics: using call numbers. #Ooooohhhh!