There's a Negative Relationship Between What People Say They Will Do and What They Actually Do
As many of us have learned the hard way, self-reported measures of buyer purchase interest (consumer or B2B, product or service) overstate the actual purchasing that will take place. People don’t do exactly what they say. Much of this overstatement comes about because the research environment assumes 100 percent distribution (all those aware of it will be able to find it easily), and 100% awareness of the concept, two conditions the company never realizes in the real world.
However, even correcting for awareness and distribution, more people are likely to say they “definitely will buy” than in fact do buy. They often overstate by a factor of 2:1. Dissimulation/prevarication/dissembling/overstatement, whatever you choose to call it, is as alive and well in “Researchworld” as it is in Washington, D.C.
We have closely examined the relationship between people’s reports on a widely heralded 11-point scale and actual buyer behavior (among people who were aware of the product and for whom the product was available to be purchased) for numerous consumer packaged goods. We have also looked at this relationship for consumer electronics, prescription drugs, new beer brands, industrial gasses, home energy services, credit cards, new television programs, new movies, new cars, package delivery services, personal computers, for the home and business markets, and business-to-business software.
Note that this scale is superior to the traditional 5- and 7-point purchase intent scales which are in common use today for several reasons
- It’s more discriminating
- More reliable
- Enhances serious thinking by respondents
- Clear interpretation across respondents
- Reminds us to deal in probabilities (not “top box” cutoffs)
- Greater validity
In our experience, usually no more than 75 percent of the people who claim that they definitely will buy actually do so. This figure declines as self-reported purchase probability declines, but the ratio is not constant. It is not linear. This leads to a set of adjustments for each level of self-report, which convert questionnaire ratings into estimates of likely behavior. The lower the “self-reported” intent, the less we believe it and we must make adjustments for overstatement.
These adjustments, as an aside, vary by the consumer’s (or B2B buyer’s) level of “involvement” in the product category. The higher the level of involvement in the product category, the more faith we can have in what people say and the lower the need for overstatement adjustment.
By taking purchase probabilities and involvement into account, it is possible to produce a reasonably valid estimate of actual sales (i.e., the percentage of consumers who would buy the product at least once).