The experts that produced ISO standard 11620:2008 have suggested that libraries should measure visits per capita as follows
- The total number of visits to the library, either physical or virtual, during a full year divided by the total number of persons in the population to be served.
- For the purpose of this performance indicator, a visit is the act of entering the library premises or accessing the library’s website in order to use one of the services provided by the library.
At the moment I am not aware of single library that has actually accepted this recommendation. The lack of implementation is easy to understand. The proposal is hard to grasp. The reason is simple. Most people experience and conceptualize physical and virtual visits as different types of entities.
- Real life visits involve planning and effort. In Norwegian public libraries physical visits typically last from from twenty to thirty minutes. Users must also spend a similar amount of time getting there – and back again.
- Virtual visits typically last a couple of minutes: fast in and fast out. The visitor does not leave her chair. She can easily visit twenty or thirty different web sites in an hour.
Combining the two is not like adding apples and pears. These are at least similar in size. It is more like adding cars and bikes, cats and mice, or trees and grasses. The entities are too dissimilar.
Statisticians do not count the number of wheeled vehicles. A category that includes buses, cars, bicycles, and prams is not socially meaningful. Biologists do estimate the number of cats and the number of mice – but they do not add tem together. Ecologists may calculate the total biomasss, but nobody in their right mind would try to measure the number of living plants in a country.
Currently the British Library has about forty visual visits per physical visit. By the ISO definition, we should say that total BL traffic has increased by a factor of forty since the arrival of the web. But nobody speaks like this.
My conclusion is: librarians, library teachers and statisticians should continue to measure physical visits (cats) and virtual visits (mice) as separate phenomena. The ISO committee should change its recommendation accordingly.
See also the page on Visits and visitors.
- Høivik, Tord. How Much is Much?: a Conceptual Study of Web Traffic. Liber Quarterly. The Journal of European Research Libraries, vol. 21 (2012), no. 2
- PL 35/12: What to do when nothing happens?
- PL 17/12: Public library indicators