Is Impulse Purchasing Really a Useful

Concept for Marketing Decisions?

DAVID T. KOLLAT

and

RONALD P. WILLETT

Impulse purchasing is animportant aspect of custom-er in-store behavior as dis-cussed in the previous ar-ticle. The authors of thispaper indicate that the con-cept, as presently employed,has limited usefulness as abasis for marketing deci-sions. They outline the prob-lems marketers must con-front in order to make theunplanned purchasing con-cept operational for market-ing decisions.

Journal of Marketing. Vol. 33 (January.1969). pp. 79-83.

66TMPULSE" or "unplanned" purchasing is a familiar term toI most business executives and marketing academicians.^ In-deed, it is common to refer to certain products as "impulse items"and or to "account for" certain kinds of behavior by classifyingit as impulse purchasing.

Unplanned purchasing is, of course, not confined to any productor retail setting. The phenomenon has been used to describe pur-chases of such products as durable goods,- jewelry, wearing ap-parel, hardware items, furniture,^ drugs and toiletries^ and groceryproducts.' Moreover, the behavior has been found to occur insuch retail settings as drugstores," supermarkets,' departmentstores, and variety and specialty stores including gift shops, flor-ists, book, barber, hardware, auto supply, lumber and furniturestores.**

While the above studies indicate that unplanned purchasing oc-curs in many types of retail outlets, it is most commonly studiedin supermarkets. The importance of this type of behavior in thisretail setting is "documented" by the latest du Pont study, whichindicates that unplanned purchasing accounts for 50rc of the prod-ucts purchased in food supermarkets."

Several kinds of retailers, particularly supermarket executivesand managers, allegedly use unplanned purchasing as a criterionfor decisions about merchandise location, space allocation and dif-

1 As used in this paper, "impulse" and "unplanned" are synonymous.- George Katona and Eva Mueller, "A Study of Purchase Decisions,"

in Lincoln Clark, editor. The Dynamics of Consumer Reactions (New-York: New York University Press. 1955), pp. 30-88.

3 Vernon T. Clover, "Relative Importance of Impulse Buying in RetailStores," JOURNAL OF MARKETING, Vol. 25 (July, 1950), pp. 66-70.

* Drugstore Brand Switching and Impulse Buying (New York: Pointof Purchase Advertising Institute, 1963).

''Consumer Buying Habits Studies (E. I. du Pont de Nemours and Co.,1945, 1949, 1954, 1959, 1965); C. John West. "Results of Two Yearsof Study into Impulse Buying." JOURNAL OF MARKETING, V'ol. 15(January. 1951). pp. 362-363; Hawkins Stern, "The Significance ofImpulse Buying Today," JOURNAL OF MARKETING. Vol. 26 (April.1962), pp. 59-62; and James D. Schaffer, "The Influence of ImpulseBuying or In-the-Store Decisions on Consumer Food Purchases"(Journal paper no. 2591 from the Michigan Agricultural Experi-mental Station).

" Same reference as footnote 4, p. 19.Consumer Buying Habits Studies (E. I. du Pont de Nemours and Co.,1965), pp. 3-4.Same reference as footnote 3, p. 67.Same reference as footnote 7.

79

80 Journal of Marketing, January, 1969

ferential promotion treatment of items. Certainstore layouts, product locations, shelf locations, andtypes of displays are apparently thought to be moreconducive to and consistent with unplanned pur-chasing than are others. Unplanned purchasing isalso of interest to manufacturers. Packaging andpoint-of-purchase decisions allegedly are based, inpart, on a product's present or potential rate ofunplanned purchasing.'"

Thus, the importance and relevance of unplannedpurchasing is apparently widely recognized and ac-cepted. However, is the concept really a usefulbasis for the types of marketing decisions that havebeen mentioned above? This article discusses fourbasic problems with unplanned purchasing thatseverely limit its usefulness for marketing decisions.First, the concept is too vague and encompasses toomany types of behavior to be an operational criterionfor marketing decisions. Second, measured un-planned purchasing rates may be exaggerated be-cause of the methodology used to generate them,and may distort the potential for increasing prod-ucts' sales by manipulation of in-store location anddisplay. Third, present measures of unplanned pur-chasing rates are misleading bases for selectingproducts for differential promotional treatments.Fourth, unplanned purchase rates for individualbrands may differ significantly from the parentproduct category rate, thereby deceiving both re-tailers and manufacturers.

The Problems of Definition

Since unplanned purchasing is a widely recognizedand frequently talked about type of behavior, itwould seem logical to expect some consensus aboutthe meaning of the phenomenon. Actually, this isnot the case, for the term is used in many differentways. The following are illustrative of the varietyof conceptual definitions:

(1) An impulse purchase is an unplanned, spurof the moment decision to purchase a prod-

(2) An impulse purchase is a logical and effi-cient way of making purchase decisions, sinceby waiting until one is in the store to final-ize purchase intentions, a more comprehen-sive and realistic evaluation of purchasealternatives can often be made.i-

1" Bert C. McCammon, Jr., "The Role of Point-of-Pur-chase Display in the Manufacturer's Marketing Mix,"in Taylor Meloan and Charles Whitlo (editors). Com-petition in Marketing (Los Angeles: Graduate Schoolof Business, University of Southern California, 1964),p. 78.

11 William R. Davidson and Alton F. Doody, RetailingManagement (New York: The Ronald Press Company,1966), p.180.

'2 Saul Nesbitt, "Today's Housewives Plan Menus asThey Shop," Nesbitt Associates Release, 1959, p. 2-3.

(3) There is no such thing as an impulse pur-chase. Rather, there are four types of un-planned purchases: (1) Pure impulse is anovelty or escape purchase which breaks anormal buying pattern, (2) Reminder impulseoccurs when a shopper sees an item or re-calls an advertisement or other informationand remembers that the stock at home is lowor exhausted, (3) Suggestion impulse pur-chasing occurs when a shopper sees a prod-uct for the first time and visualizes a needfor it, and (4) Planned impulse purchasingtakes place when the shopper makes specificpurchase decisions on the basis of price spe-cials, coupon offers, and the like.'^

Field studies of unplanned purchasing have em-ployed still other operational definitions. The fol-lowing are illustrative:

(4) Shoppers are questioned upon entering thestore as to what they plan to purchase andrecords are made of what they do in fact pur-chase. Those items purchased but not men-tioned during the first interview are impulsepurchases.!••

(5) Impulse purchasing is the difference in pur-chases between a sample of customers re-porting actual purchases (exposed to in-storestimuli) and another sample of customers re-porting what they anticipated buying while

Hawkins Stern, "The Significance of Impulse BuyingToday," JOURNAL OF MARKETING. Vol. 26 (April,1962), p. 59.Same reference as footnote 7, p. 2.

• ABOUT THE AUTHORS. David T.KoUort is an Associate Prolessor of Mar-keting at The Ohio State University. Di.Kollat has published articles in the Jour-nal ot Marketinq Research, the Proceed-ings of the American Marketing Associ-ation, and has been a contributor to theEjicyclopaedia Britannica. He is coau-thor of Consumer Behavior and Casesin Consumer Behavior and is also a co-author of a forthcoming book Researchin Consumer Behavior.

Ronald P. Willett is Associate Profes-sor of Marketing and Assistant Chair-man. Marketing Department, IndianaUniversity. He holds BS and MBA de-grees from Miami University (Oxford)and his DBA is from Indiana University.

Dr. Willett is currently Director of thePharmacists Buying Behavior Study andCo-director of the Family Behavior Re-search Project at Indiana University.His articles have appeared in the JOUR-NAL OF MARKETING and the Journal ot Marketing Research.

Is Impulse Purchasing Really a Useful Concept for Marketing Decisions? 81

sitting in their living rooms (not exposed toin-store stimuli) .'^

(6) Impulse purchasing is the difference in astore's sales volume during weeks in whicha holiday occurred with the week immediatelyfollowing during which a holiday did notoccur.'̂ ^

From the above, it appears that there are con-siderable differences of opinion as to what is meantby an impulse purchase.'" Conceptual definitionsdiflfer not only in degrees of precision but, morebasically, in terms of the amount and type of deci-sion making that is involved, and, by implication,the susceptibility of the behavior to marketer strat-egies. Similarly, there is considerable variation inthe way in which impulse purchasing is empiricallydefined. Finally, and perhaps most importantly,there are conspicuous differences between conceptualand empirical definitions.

The lack of consensus about the meaning of im-pulse purchasing would seem to limit the usefulnessof the concept. The different definitions used inempirical studies make it difficult to compare find-ings and accumulate information about the natureof the behavior. Moreover, the marketing implica-tions of impulse buying sometimes vary accordingto which definition is adopted. For example, ifdefinition (1) is accepted, it may be advantageousto periodically relocate products having high un-planned purchasing rates in order to increase cus-tomer exposure. In contrast, if definition (2) isaccepted, this strategy may not be desirable partic-ularly if the location(s) is inconsistent with whereshoppers typically look for the product (s).

Finally, and perhaps most basic, it is questionablewhether intelligent piarketing decisions can bemade about how to influence unplanned purchasingwhen there is so little agreement about what thephenomenon is or what it involves. That is, howcan profitable strategies be devised when the objec-tive—to influence impulse purchasing—is so poorlydefined?

Impulse Purehasing—Fact or Artifact?

There are differences of opinion about why im-pulse purchasing occurs. Two conflicting explana-tions are: (1) the exposure to in-store stimulihypothesis: and (2) the customer-commitmenth>-pothesis.

'••̂ James D. Schaffer, "The Influence of Impulse Buyingor In-the-Store Decisions on Consumer Food Pur-chases" (Journal paper no. 2591 from the MichiganAgricultural Experimental Station).

'* Same reference as footnote 3. p. 68.'̂ For other definitions of impulse purchasing, see How

People Shop for Food (Market Research Corporationof America, undated manuscript) ; One On The Aisle(New York: Life Marketing Laboratory, undatedmanuscript) ; and Impulse Buying (Philadelphia: TheCurtis Publishing Company Research Department,February, 1952).

The Exposure HypothesisAccording to this hypothesis, exposure to in-store

stimuli produces unplanned purchases because: (1)shoppers use product assortments and other in-storestimuli to remind them of their shopping needs;that is, shoppers make some purchase decisions inthe store rather than relying solely on a shoppinglist; and/or (2) in-store promotional techniquesresult in shoppers recognizing new ways of satis-fying needs.

Several studies have indicated that in-store stim-uli can trigger unplanned purchases. For example,it has been demonstrated that the store location ofsuch products as bread, milk and dairy products isinstrumental in precipitating unplanned purchasesof surrounding products."* Point-of-purchase dis-plays, signs.^'-' and shelf extenders'-" are illustrativeof other promotional techniques that have, in someinstances, proven effective in stimulating impulsepurchases.

However, increasing product exposure does notalways increase the rate of unplanned purchasing.For example, one study has shown that some prod-ucts with relatively high impulse purchasing rates(Tang, hominy, powdered coffee cream) are not moreresponsive to increases in shelf space than the salesof products having relatively low impulse purchasingrates (baking soda).-' Moreover, in some instances,end-aisle displays of relatively high impulse prod-ucts (pie crust mix and apple pie filling) do notproduce greater direct product profits than the end-aisle treatment of relatively low impulse products(spaghetti and spaghetti sauce) .-'-

Thus, contrary to what seems to be the opinionof many marketing academicians and practitioners,exposure to in-store stimuli triggers only some un-planned purchasing, not all of it. The rate of un-planned purchasing appears to depend on the typeof stimulation technique, the product that is being

1* Lawrence W. Patterson, In-Store Traffic Flow (NewYork: Point-of-Purchase Advertising, Institute, Inc.,1963), p. 2.

'^ See, for example. 4̂ First Study of Totality of Impactof Point-of-Purchase Material on Plus Sales in Super-markets (New York: Point-of-Purchase Advert is ingInst i tute , Inc., 1959), p. 18; Drugstore Brand Siritch-ing and Impulse Buying (New York: Point-of-Pur-chase Advertising Inst i tute , Inc., 1963), p. 10; Pack-age Store Brand Sw-itching and Impulse Buying (NewYork: Point-of-Purchase Advert is ing Inst i tute , 1963),p. 10.

-*" Samuel Rouda, What Today's Supermarket ChainsExpect from Manufacturers in Promotional Support(New York: Point-of-Purchase Advert is ing Ins t i tu te ,1957), p. 64.

21 Keith Cox, "The Responsiveness of Food Sales toShelf Space Changes in Supermarke t s , " Joumal ofMarketing Research, Vol. 1 (May, 1964), pp. 63-67,at p. 64.

22 Robert F . Kelly, "An Evaluat ion of Selected Variablesof End Display Effectiveness" (unpublished DoctoralDissertat ion. Harva rd Universi ty , 1965), p. 50.

82 Journal of Marketing, January, 1969

promoted, and the customer who selectively exposeshimself to, and selectively perceives, the promotionalstimuli. If in-store stimuli do not precipitate allunplanned purchasing, then it follows that otherfactors must be causing some of this type ofbehavior.

The Custonter-commitment HypothesisThe customer-commitment hypothesis maintains

unplanned purchasing, or differences between pur-chase intentions and actual purchases, are attribut-able, in part, to incomplete measures of purchaseplaris. "Measured purchase intentions" are not thesame as "actual purchase intentions" because theshopper is iinicilling and/or unable to commit thetime and/or cognitive resources necessary to makethe two types of purchase intentions equivalent.

The customer may be ununlling to itemize herpurchase intentions because she does not want toinvest the amount of time and thought necessaryto give the interviewer a complete roster of herpurchase plans. Instead, she articulates only anincomplete itemization of what she plans to purchase,thereby satisfying the requirements of the interviewwithout spending too much time or having to thinktoo much.

There are several reasons why the shopper may beunable to itemize her purchase plans. First, theshopper may know what she will purchase but maybe unable to articulate these purchase intentionsbecause of the characteristics of the interview.The methodology used in most .studies of unplannedpurchasing forces the shopper, in the absence of ashopping list, to rely on memory for purchase in-tentions. In other words, unaided and nearly spon-taneous recall is usually used to measure purchaseplans. Thus, the methodology alone guarantees thatmeasured purchase plans will deviate to some degreefrom actual purchase plans.

Second, the shopper may know what she will pur-chase but may be unable to relate these intentionsregardless of the amount of assistance given by theinterviewer. That is. without exposure to in-storestimuli, the shopper may be unable to constructcognitively and verbalize for the interviewer whatshe will purchase.

The logic underlying the customer-commitmenthypothesis was alluded to nearly two decades ago.-'-̂The hypothesis was also deduced from a recent studyof the unplanned purchasing behavior of 600 super-market shoppers.-'^ Since the hypothesis was a by-product rather than an objective of the study, itwas not pos.sible to determine the amount of un-

-'3 William Applebaum, "Studying Customer Behaviorin Retail Stores," JOURNAL OF MARKETING. Vol. 16(October, 1951), pp. 172-178, p. 178.

~* See, David T. Kollat and Ronald P. Willett, "CustomerImpulse Purchasing Behavior," Journal of MarketingResearch, Vol. 4 (February, 1967), pp. 21-31.

planned purchasing caused by the phenomena com-prising the hypothesis.

ImplicationsTo the extent that unplanned purchasing is at-

tributable to the customer-commitment hypothesis,unplanned purchasing is not unplanned at all, butrather an artifact of the way in which the behav-ior is measured. Consequently, true unplanned pur-chase rates are considerably lower than these thatare currently accepted. That is to say, pre-shoppingdecisions about products and brands to be pur-chased are more common than past studies haveindicated.

The evidence presented indicates that presentlyaccepted rates of unplanned purchasing-' may ex-aggerate the potential for influencing buying deci-sions. As a consequence, promotional expendituresdesigned to increase the rate of unplanned purchas-ing may be excessive. Conclusions concerning thedegree of excessiveness must be postponed until thequantitative impact of the customer-commitment hy-pothesis is determined.

Promotional Implications

Retailers sometimes use product unplanned pur-chasing rates to select products for differential pro-motional treatments. Such decisions as store loca-tion, shelf height, number of shelf facings, and end-aisle treatment for specific products are often based,in part, on product unplanned purchase rates.

Since some unplanned purchasing is not unplannedat all, but an artifact of the way in which the be-havior is measured, trve unplanned purchasingrates are considerably lower than those that arecurrently accepted. It seems risky to assume thatall product unplanned purchasing rates are inflatedto the same degree; rather, some product rates areprobably overstated more than are others.

Research to date does not facilitate measuring theextent of distortion of unplanned rates across prod-ucts but the direction of bias can be suggested.Based on the customer commitment explanation thebias in unplanned rates is likely to be high for itemsthat are discretionary rather than staple, or havelow frequencies of purchase or have highly variableinterpurchase time periods. These same character-istics are purported to be determinants of unplannedpurchase rates. Hence, product categories with highmeasured unplanned purchase rates are also likely todemonstrate greater measurement error, and con-versely, products with low unplanned purchase ratesexhibit smaller amounts of error. As a consequencethere may be a smaller range between productspurported to have high and low unplanned purchaserates, and the use of these rates as a single criterionfor assignment of promotional effort may be ques-tionable.

Same reference as footnote 7, pp. 3-4.

Is Impulse Purchasing Realty a Useful Concept for Marketing Decisions? 83

Thus, although direct empirical evidence is notavailable, from the evidence presented above it ap-pears legitimate to deduce that existing unplannedpurchase rates are likely to be misleading bases forselecting products for promotional efforts.

Product Category Rates May Be MisleadingUnplanned purchasing rates are typically reported

by product category.-* It is often dangerous to as-sume that a specific brand's unplanned purchasingrate is equal to the product category average.

In one instance studied, for example, a food prod-uct category had an average unplanned purchaserate of b\^c. Although most of the brands in thiscategory had unplanned rates approximating bl'^'c,the unplanned rate for one major brand was only26%.27

For reasons already mentioned, the above figuresmay not represent the true unplanned rates. How-ever, for purposes of discussion, assume that theyare correct. If so. then the product category ratemay be misleading to both retailers and manu-facturers.

If retailers fail to recognize that the unplannedrates of individual brands may differ significantlyfrom the product category rate, then, all other thingsbeing equal, they are likely to be indifferent as towhich brand within a product category is given spe-cial promotional treatment. In the above case thismay be a mistake, since sales of the brand havingthe lower unplanned rate may be less responsive tosome special promotional efforts. Thus, basing pro-motion decisions on product category averages ratherthan the individual brand's unplanned purchase ratemay cause retailers to promote the wrong brand.

Product category rates may also be misleading tomanufacturers. In the above case, for example, themanufacturer of the brand having an unplanned rateof 26<^ may want to know why his brand has sucha relatively low rate. Does it mean that he is doinga competitively superior job of creating brand aware-ness and generating pre-shopping brand choice, butis not getting his share of in-store purchase deci-sions? Why is he not getting a competitive shareof in-store purchase decisions? The point, of course,is that the manufacturer cannot ask these kinds ofquestions and obtain whatever additional profits theanswers might yield if he fails to remember thatindividual brand rates of unplanned purchasing maydiffer significantly from product category rates.

Toward an Operational Concept ofImpulse Purchasing

How Unplanned Purchasing Can Become aUseful Concept for Marketing Decisions

From the discussion above it is apparent that sev-

2̂ Same reference as footnote 7, pp. 3-4."David T. Kollat and Ronald P. Willett, "Interbrand

Variation in Unplanned Purchasing Rates" (unpub-lished working paper, April, 1966).

eral problems must be overcome before unplannedpurchasing can become a useful concept for market-ing decisions. First, the concept must be preciselydefined. Since the value of the concept hinges inlarge part on empirical studies of the extent andnature of the behavior, it seems desirable to adopta definition used in empirical studies, providingthat it is capable of yielding managerially relevantinsights. Second, a series of methodological studiesneeds to be conducted in order to devise a measuringinstrument and process that will equate measuredand actual purchase intentions. Space limitationsprohibit a detailed presentation of such studies here.In general, however, it would appear useful to de-termine experimentally the effects of interviewercueing and customer incentives on the rate of un-planned purchasing. Experimental manipulation ofinterviewer cueing would attempt to determine theextent to which inability to itemize purchase inten-tions artificially "creates" subsequent unplanned pur-chasing. Various levels and types of incentives couldbe used to overcome customer unwillingness to artic-ulate purchase intentions. Finally, unplanned pur-chasing rates need to be computed for individualbrands as well as product categories.

Overcoming these problems will involve a substan-tial commitment of time and resources. However, thepotential value of true rates of unplanned purchas-ing may exceed the costs of obtaining them. Whentrue rates are determined, other categories of plan-ning—specifically planned, generally planned, andbrand substitution—would probably differ, both inmagnitude and in relative occurrence, from thosethat are currently accepted. These refined measuresof various types of in-store decisions would providemore sensitive indices of the amount and type ofpromotional effort that should be allocated toproducts.

Refined measures of unplanned purchasing wouldpermit a partial functional analysis of the strengthsand weaknesses of a firm's promotional program.For example, if unplanned purchasing were definedand measured in such a way as to be equivalent toin-store purchase decisions, a manufacturer coulduse rates of unplanned purchasing for his brand (sias a criterion for evaluating the effectiveness of bothhis advertising and in-store promotional strategy.

Pure measures of unplanned purchasing and othercategories of planning would constitute one of themost potentially meaningful indices of the real effectsof specific in-store product promotions. For example,the difference in a product's unplanned purchase ratebefore and after a special in-store promotion couldbe used by the retailer as a measure of the effective-ness of that strategy. Other planning categoriescould also be used in this manner. These measuresof effectiveness seem particularly useful since theyindicate both the type and extent of behavioralchange precipitated by an in-store promotionalstrategy.