JOHN PHILIP JONESSyracuse UniversityWhat Does Effective Frequency Meanin 1997?THE WORDS"EFFECTIVEFREQUENCY"IMPLYMORE thanthey directly convey. In literal terms, effective fre-quency can mean that a single advertising expo-sure is able to influence the purchase of a brand.However, as all experienced advertising peopleknow, the phrase was really coined to communi-cate the idea that there must be enough concentra-tion of media weight to cross a threshold. Repeti-tion was considered necessary, and there had to beenough of it within the period before a consumerbuys a product to influence his or her choice ofbrand.DID IT AU BEGIN IN 1979?The idea is rooted not so much in research as incommonsense: the instinct to use advertising toknock consumers repeatedly over the head. Con-centration-spending money in “flights” or“bursts’‘-is a policy as old as television advertis-ing itself. I have personally seen it in practice forfour decades. As far as operational policy was con-cerned, there was therefore nothing new in thestrategy advocated by Michael Naples in themonograph he edited and published in 1979, Ef-fective Frequency: The Relationship Between Frequencyand Advertising Effectiveness. This work did, how-ever, provide an imprimatur: a stamp of academicrespectability for a virtually universal practicewithin the advertising industry.In Naples’s terms, Effective Frequency meantthree opportunities-to-see (OTS) within the pur-chase interval. Hard data do not exist to demon-strate how widely this policy has actually beenfollowed since 1979, or at least had been followedduring the 15 years since Naples’s book came outwhen a new notion, Continuity Scheduling, beganto be propagated. But anecdotal evidence and myown personal observations both suggest that theEffective Frequency strategy was being imple-mented by 90 percent of packaged-goods advertis-ers in the United States. Few doctrines have influ-enced professional practice in the advertising field14 JOURn!t OF !~ilERTlSlnG RESEARCH July . August 1997to such an extent, although we must of course re-member that most advertisers were planning forEffective Frequency before the Naples book camealong to tell them that they were doing the rightthing. It is in fact Continuity Scheduling that rep-resents the real innovation, and this is the mainsubject of this article.Naples’s monograph provided a valuable ser-vice in publishing in succinct form the most salientevidence bearing on the issue of Effective Fre-quency. Nevertheless, three parts of the bookeventually generated rather serious debate, al-though it was some time before any doubts wereraised.The first concerned Colin McDonald’s research.Much reliance was placed on this important pio-neer experiment with the use of consumer diaries(McDonald, 1979) and which employed a type ofsingle-source research that I subsequently de-scribed as the pure single-source method (Jones,1995). (See the Glossary at the end of this article.)McDonald’s work provided the strongest empiri-cal underpinning in Naples’s book. But it was tooeasily forgotten that this research was, despite itsoriginality and virtuosity, merely a small-scale ex-periment carried out a number of years previouslyin a foreign country.The most striking-and disturbing-finding ofMcDonald’s investigation was that his advertisingresponse function appeared to have the shape ofthe curve shown in Figure 1. What McDonald wassaying was that one advertising exposure actuallydepressed sales. If this conclusion could be properlysupported, it is difficult to think of anything morelikely to alarm advertisers who might have beenconsidering deploying their budgets with a sub-threshold degree of concentration.What is now perfectly clear is that this remark-able response function is an artifact of McDonald’sstatistical method. He relied on brand-switching tothe exclusion of repeat purchase as his criterion ofeffectiveness. Brand-switching of course tells onlyFAFih;hiluWinthETfelin(J(d;inadofDcteiPCthW(caPllhethlaltia“VansuSt2AdvertlslngFigure 1 McDonald’sAdvertising ResponseFunctionhalf the story. Moreover, the data from allhis brands were aggregated: he had tolump together the ineffective campaignswith the effective ones, since he was work-ing with too small a sample to analyzethem separately. These two factors to-gether managed to mask the positive ef-fect of one exposure and to turn a salesincrease into an apparent sales reduction(Jones, 1995a). When he recomputed hisdata to measure a straightforward changein share of market, pre- and post-advertising, McDonald produced a curveof diminishing returns (see Figure 2) (Mc-Donald, 1994). This showed that it was af-ter all viable-indeed economic-to ex-pose a single advertisement; there was nothreshold before advertising began towork. This of course had a serious impli-cation for the Effective Frequency doctrine.The second controversial part of Na-ples’s monograph was the extent to whichhe relied on Herbert Krugman’s cognitivetheory. Krugman plausibly hypothesizeda hierarchy of effects from three sequen-tial advertising exposures: (1) to prompt“What is it?“; (2) to prompt “What of it?“;and (3) to remind (Krugman, 1972). Con-sumers have to move through all threestages for the campaign to influence them.10man’s doctrine is that it only applies tounfamiliar advertising campaigns. Ittherefore operates in exceptional and notnormal circumstances. Krugman makes ittotally clear that, with established and fa-miliar campaigns, any isolated repeat ex-posure acts as a reminder of the second-which may have been perceived by theviewer at an earlier time. In other words, asingle exposure can operate effectively aspart of an ongoing campaign because ittriggers a recollection of advertisementsexposed when the campaign was first in-troduced and when viewers were beingeducated about its meaning. This againcast a serious shadow on the Effective Fre-quency doctrine.The third disputable point about Na-ples’s book is its discussion of the pur-chase cycle. McDonald’s research exam-ined the effect of incremental advertisingstimuli within this cycle-the period be-tween last purchase and next-a method-ologically sound procedure.However, the purchase cycle intervalwas badly misapplied to the process ofmedia planning. Media planners appreci-ated that the cycle is more or less uniformbetween different buyers of any brand.However, they unconsciously assumedthe same timing for these intervals.