Gross Impressions

Gross impressions are widely used in program eval-uaion to indicate the number of people potentially exposed to a media message. These numbers are based on circulation figures for print media and ratings figures for broadcast media. Gross impressions are calculated by multiplying the number of messages that appear by the appropriate circulation or rating. The gross impressions number can become very large, very quickly; however, it must be used with care. The main caveat that should always be stressed is that these are potential expo-sures, not actual numbers of people who read, viewed, or heard the message. The classic example is Super Bowl commercials. Air time during the game sells for very high sums based on the poten-tial audience exposure. But people are known to do many things during commercial time aside from watch the commercials (for example, go to the refrigerator or restroom). Thus, actual exposures are typically lower (and sometimes greatly so) than gross impressions for TV messages. The opposite might actually be true of print media. One newspa-per in a library or periodical in a doctor's office will likely have far more than one reader. And with the current proliferation of cafés in bookstores, count-less newspapers and periodicals are read but not purchased. Thus, circulation figures can actually underestimate the number of people exposed to a print message.

Another problem with the gross impressions number is that although it may provide some idea of the number of people exposed to a message, it says nothing about whether those exposed were part of the actual target audience. This issue is partly addressed by choosing appropriate media place-ments, but few media sources, especially major out-lets, provide the precise targeting public relations often desires. One way to ameliorate this problem somewhat is to develop an overall promotion and publicity effort that generates a “buzz” about a topic. For example, movie promotion is very involved these days. Trailers and product tie-ins create awareness and anticipation. Then a star hits the talk show circuit to talk about what she's doing in her life, and just happens to mention her latest movie that opens in a few days and has a clip or two from it. People who like the star and are thus likely to go to the movie see the interview on Leno. They will talk to friends at work the next day, and those people may well be more inclined to watch the star [Page 377]on Letterman the next night. The overall promotion effort thus enhances the impressions generated among the most desirable audience members.

Finally, simple exposure says nothing at all about the impact or effect of a message. Use of the gross impressions figure alone is very misleading as a measure of the effectiveness of public relations activities. Meaningful program evaluation must always measure impact, not simply potential.