How are radio audiences measured?

The front of a RAJAR diary.

A RAJAR diary is A5-sized, with around 50 pages. There are two pages for each day of the week, with the time in 15 and 30 minute periods down the side.

There are also some tick-box questions at the front, relating to the respondent's general radio usage, use of the internet, cinema and newspapers, and television viewing. These are very useful for monitoring more general trends of media consumption.

A card fold lifts up from the front cover when opened, and the respondent is asked to choose from some accompanying stickers which radio stations he or she has heard in the last year or so.
These stickers are then put on the card fold (see left), which is then visible over each of the days' grids. All of the national stations and the local services available in the area are included.

The respondent is asked to draw a line downwards through the boxes from when they start listening to a station until they stop. An 'X' is then added at the start of the line and another 'X' at the end, to make the listening period clearer. So in the example on the right, the line shows that the respondent was listening to BBC WM on a Monday evening between 4.30 and 6.15 PM.

This line would then mean that:

• The respondent would be counted as having been listening to BBC WM at these times
• The respondent would be counted in BBC WM's weekly reach
• The time spent listening here would count towards BBC WM's share of listening to all radio.

The diaries are collected and processed, and then every three months a quarterly set of audience figures for each station is released. Where a station is local rather than national, it is able to find out how it has done in its particular transmission area, rather than being lost in the national figures.