All over the world, libraries tend to gather data about users by counting the number of library visits. Visits are either registerede automatically, by electronic counters at the entrance, or manually, by direct observation.
Let us look more closely at the concept of library visits.
Concepts and measurements
Concepts and measurements are not the same thing.
Take electronic counters as an example. They do not measure visits as such – they count how many times an electronic beam has been interrupted. The counter does not distinguish between an ordinary visitor, a staff member, a big dog – or a child who runs in and out ten times in a row.
A genuine library visit, I would say, starts when a person enters the library premises in order to use one or more of the library services. A library visit ends when the person leaves the premises.
A single visit corresponds to two “hits” or steps on the counter: one when the user enters and one when the user leaves.
But if the person only leaves for a few minutes, to buy a soft drink or make a phone call, she (or he) would not say that she visited the library twice. In social terms, a single library visit may include brief excursions outside.
A person who pops into the library to use the bathroom, would not speak of this as a library visit either. A real library visit is defined by its purpose.
A visit to the library is a social concept.
It is defined by the way we understand and use it in daily life. An electronic counter is an instrument for counting the number of library visits. But the instrument is not perfect. Very few instruments are.
An electronic counter will normally give values that are a bit too high – because the counter catches some events – entrances and exits – that do not correspond to library visits in the ordinary social sense.
If people enter in groups, it may also miss some visits. Two or more people walking close together will often be counted as just one person.
To get more accurate data from a counter, we need to calibrate the counter. That means comparing electronic and manual data – and to calculate a correction factor.