Advertising Effectiveness

The advertising industry, as a whole, has the poorest quality-assurance systems and turns out the most inconsistent product (their ads and commercials) of any industry in the world. This might seem like an overly harsh assessment, but it is based on testing thousands of ads over several decades. In the author's experience, only about half of all commercials actually work; that is, have any positive effects on consumers' purchasing behavior or brand choice. Moreover, a small share of ads actually appears to have negative effects on sales. How could these assertions possibly be true? Don't advertising agencies want to produce great ads? Don't clients want great advertising? Yes, they do, but they face formidable barriers.