NOoIw == 5 HOW MUCH DO PEOPLE USE THE LIBRARY? ALTHOUGH IT IS CONVENIENT to set up an arbitrary defi- nition of “radio listener” or “movie goer” or “book reader,” this does not mean that individuals within these groups make equal use of communication media. Not all “radio listeners” listen the same amount or to the same kinds of program, and not all “book readers” read the same number or kinds of books. Up to this point we have dealt with these groups as homogeneous units for purposes of general description and analysis. Let us now refine our concept of exposure to the five major media of communication, as an introduction to an analysis of the concentration of library use. CONCENTRATION-DISPERSION OF USE AMONG THE MAJOR MEDIA OF COMMUNICATION There are differences in the intensity or frequency of use for each of the media. Some people spend much time reading, or viewing, or listening, and some only a little (even though all may qualify as users under the broad definition). This accounts for what may be called “concentration-dispersion” of communication expo- sure, that is, the unevenness with which the total amount of exposure is distributed among the members of the audience. If every movie goer saw the same number of films, then there would be no concentration of exposure in that medium. But if a relatively few members of the audience went to the theater very frequently and the rest’only seldom, there would be high concentration of exposure. Actually, there is some