Understanding and quantifying the benefits of advertising is a problem as old as advertising itself. The problem stems from the many purposes advertising serves: building awareness of products, creating brand equity and generating sales. Each of these objectives is not easily measured or related to the advertising that may have affected it.
First, there has been an explosion in media alternatives from the traditional standbys of television, radio and print into a broader spectrum of both offline and online options, with the Internet clearly the most visible example of this change. The choices within each medium also have expanded in an attempt to reach more targeted audiences.
Television, for example, has burgeoned from three primary networks to literally dozens of mainstream cable channels, all capable of reaching large audiences with brand messages or product promotions. Hundreds of new magazines now serve many special interest groups, while Web advertising presses the edge of one-to-one marketing.
In addition, more and more companies are using integrated, multimedia strategies to reach their desired audiences, layering broadcast advertising over direct response campaigns or combining online with offline campaigns. All of this is making it harder to separate out the individual influences of each advertising effort.
http://www.dmnews.com/pdffiles/ryan.pdf
