As advertising professionals assess the strengths and weaknesses of various media vehicles, one of the major benefits cited for print vehicles is the medium's portability. The consumer does not have to be seated in front of a TV, drive by a billboard, or be on-line at a computer. Magazine copies travel through time and space as they build their total audiences.

Advertising buying decisions are most frequently based on a magazine's total reach of a desired target audience and the cost efficiency of reaching that target. Of course, there are several other buying criteria that are important including editorial relevancy, magazine vitality (growing circulation, consistently meeting or exceeding rate base, reader affinity scores, total audience trends), composition of the desired target, ad positioning, and marketing or added value programs.

The cornerstone, however, of the buying process starts with total audience. Given the portability of magazines, several people have the opportunity to (and do) read a singular issue. In fact, according to historical MRI data, the average issue of the major magazines measured by their service is seen by four people. In the industry vernacular, this is what is meant by "readers per copy".