Much of the early but still influential thinking around optimal frequency stems from Herbert Krugman. While at GE in the 1960s, Krugman developed the “three hit” theory of frequency. It said that consumers needed to be exposed to an ad three times for it to be effective. Michael Naples’ work in 1979 supported Krugman’s claim but added a few nuances. For one, he concluded that less well-known brands require more frequency. Then, in 1982, Joseph Ostrow outlined several marketing factors that impact which frequency is optimal, Including brand share level, length
of purchase cycle and the nature of the target audience. Read the article.