How does a radio station measure the number of listeners?

At the CIM, February, May and August are the favorite months of the radio stations. Three times a year the CIM publishes the listening figures of the radios in Belgium. In each of these three survey waves, approximately 8,000 people are invited to complete an audio diary for 7 days. They fill in which radios they have listened to per 15 minutes.

The participants are recruited through a face-to-face interview at home. They are randomly chosen among all individuals aged 12 and over.

This study is being carried out by GfK Belgium.

The CIM TV study measures television viewing in Belgium in a continuous and standardized manner. To this end, the CIM works together with the research institute GfK and Nielsen. For the TV measurement, the CIM calls on a panel of 1,500 families. An audiometer or viewing meter is installed in each of these families. This device registers the viewing behavior of the various members of the family, and any guests who register as viewers. In total, the panel represents approximately 3,700 people.

Today, the CIM not only measures viewing of television programs at the time of broadcast. Programs that are (re)watched up to and including 7 days later are also identified. The viewing meter also registers all other uses of the TV, such as watching DVDs, gaming, viewing photos, and so on.
Every day, the more than 60 participating channels and the advertising world receive detailed figures about the TV viewing of the previous day. The broadcasters use it to evaluate and optimize their programming. The advertising world uses it to buy and sell advertising space, and to measure the reach of advertising campaigns. The program viewing figures for the general public, which are published daily or weekly in newspapers and magazines or on the Internet, are also based on the CIM TV study. On this site, the public results section shows a preview of the ratings for the past week, the past month, and the past year.