Research Organisations

BARB

The Broadcaster's Audience Research Board is an organisation that provides viewing figures of television programmes. They are used by the BBC and independent broadcasters so they can see estimates of how many viewers they have and at specific times, also providing a breakdown of the type of viewers that are watching. Their data is primary as they get it from panels of viewers and their data represents the viewing behavior of more than 25 million households in the UK.
This information is really important for the broadcasters because to be commercially viable they need to know what their audience like and don't like and who will want to watch what. If they broadcast something that gets a lot of viewers then they might decide to broadcast it more often and if it doesn't get many viewers then they might decide to cancel it or not show it again.

NRS

The National Readership Survey is a non-profit organisation that provides information on what type of people read which publication, and they have broken it down according to age, gender, social class and other lifestyle characteristics and demographics. Their work covers more than 250 newspapers, newspaper supplements and consumer magazines and is made available online.
The data that NRS produce is very important because other organisations who intend to buy or sell advertising in publications can figure out where the right place to do it is so that they will get the right audience.

ABC

The Audit Bureau of Circulation provide information about the circulation of newspapers and magazines, much like the National Readership Survey, but also researches more products like leaflets, exhibitions, directories, and websites.
It is important for the same reason as NRS, and was originally launched so that the claims made by publications about their readership and circulation could be verified by the advertising industry.

RAJAR

The Radio Joint Audience Research Limited provides estimate numbers of the amount of people who listen to radio programmes including the BBC and other UK commercial stations. The BBC own RAJAR along with the Commercial Radio Companies Association (CRCA).
This is helpful again for advertisers, so they can decide which station to advertise on, and as well for what the radio stations to decide what they should and shouldn't broadcast.