As with print and broadcast media, a contact and distribution measurement is also required for the World Wide Web. In the field of print media, circulation is calculated. In principle, the instrument is fairly simple. The publishing houses that wish to claim audited circulations register their circulations, as evident in their bookkeeping, with an ABC (Audit Bureau of Circulation). In Germany, the only institution of this kind is called IVW (Information Organization for the Registration of the Distribution of Advertising Vehicles). For their part, the ABCs publish the numbers and inspect the data. In some countries the data is available on a cost basis, in others the data is free of charge. This is a total census. The results are often referred to as a value for calculating advertising rates, yet, in the case of audience research, only provide marginal indications (see McQuail, 1998).