Now that we've talked about using publication dates, let's talk about metrics that use call numbers. What do we still have in the collection after that big weed? It's too big a chart to include here, but I can tell you that the top three subject area holdings in my 500s are:
1. 599 Mammals - 161 items
2. 551 "Geology, hydrology, meteorology" - 153 items
3. 523 "Specific celestial bodies and phenomena" - 139 items.
Now we need to find out where the holes in the collection are. Still sorted by call number, we look at the subject areas that have very few holdings and decide if they are popular enough to warrant buying more items in those areas. There isn't necessarily a lot of quantitative data to help you make this decision. I feel like I'm aware enough of my community's needs (curriculum, local clubs, common reference questions, collection policy) to make an educated guess about what subject areas we need more materials in and which ones we don't. We also have collection management guidelines and a selection policy to follow.
The bottom three subject area holdings in the 500s are:
1. 562 Fossil invertebrates - 1 item
2. 565 Other fossil invertebrates - 1 item
3. 596 Vertebrata - 1 item
We have plenty of items on vertebrate fossils, but apparently very little on invertebrate fossils. Ok, we'll try to buy a few.
Working up from the bottom of the holdings list, some subjects we are lacking in that might be worth purchasing more:
Sound and related vibrations - currently have 0 items
Heat - 2 items
Magnetism - 2 items
Invertebrates (not fossils, but live ones) - 3 items
Light - 3 items
Physical anthropology - 4 items
Evolution and genetics - 5 items
Earth (astronomical geography) - 5 items
Topology - 6 items
Biology - 7 items (we have 17 in life sciences, though. We're not an academic library, so that is an important distinction. We should have more in the broader category.)
The next step for the lucky Intern is to buy some new materials to flush out these areas. It could be tricky to find some titles in these subject areas that are public library appropriate and not too academic. We also have to remember that we have access to inter-library loan and a wealth of databases that include science encyclopedias and journals.
That's how I use call number metrics to see what we have and what we need!