The 75% Solution

According to an excellent white paper entitled Library Stacks and Shelving, [written by Earl Siems and Linda Demmers and provided through the Libris Design Project [http://www.librisdesign.org], supported by the U.S. Institute of Museum and Library Services under the provisions of the Library Services and Technology Act]:

"Optimum capacity for a working collection requires shelves that are only 70-75% full. This extra space is not considered future growth space, but is the space required for collection management, efficient reshelving, interfiling of new acquisitions, and multi-volume sets."

Using this benchmark, a standard 36" wide, 90" high, dual-facing section of metal shelving should optimally contain:

• 336 fiction titles (at 8 per linear foot)
• 252 scientific/technical titles (at 6 per linear foot)
• 420 non-fiction titles (at 10 per linear foot)

This means that, on average, there should be 9" of free space on each 36" shelf, to assure efficient management of the print collection--i.e., to allow reshelving to proceed quickly, and to avoid constant shifting of crowded sections of the stacks. Take a walk through your own collection with this in mind.

This also suggests a target for deselection projects and perhaps one kind of metric for a sustainable collection. A sustainable collection is one that keeps stacks at 70-75% of their nominal capacity. Something that looks like this:


rather than like this:

In addition to reducing labor for shelving and shifting, the 75% rule also provides a better browsing experience (to the degree that users are still browsing!), and reduces the risk of damage to items in the collection.