There can be no advertising network without a research network, no media and no campaigns without a fixed apparatus of evaluation, both quantitative and qualitative, of audiences and targets.

The end of the era of rationed advertising space has upset established ways of conceiving the audience and its measurement. Media-buyers like the agencies must provide advertisers with sharper information in order to direct their investment in television more effectively. In the highly speculative context of an explosion in the supply of advertising space, data on audiences must justify the accuracy of this or that placement. Observation of the ebb and flow of audiences, programmes and products has therefore entered a new phase. To grasp this shift the better first requires a little archaeology, a review of the period which is now coming rapidly to a close.