Measuring the audience

The publishers of any media text are concerned about measuring their audience share so that they can judge the effectiveness and reach of their product. To do this the publishers employ research companies like ACNeilsen, Colmar Brunton and others to survey the consumers and to extrapolate the audience reaction and interest.
The processes are discussed in "MEDIA STUDIES - Achievement Standards Level 2". pp 3-40.
The following links will take you to specific research companies, agencies their reports , recommendations and the data they produce from this research.
Audience measurement theory
ACNeilsen How it's done
Neilsen & ethnic audiences
Colmar Brunton
Methods of measurement
Measuring readership
emap advertising solutions (UK)
Advantages & disadvantages of targeting media audiences (essay)
Does audience or ownership influence media?