Technical Note—Aggregating Individual Purchases to the Household Level

Household level panel data are the input for many types of marketing studies. An interesting, but until now unaddressed, question is what is the effect of aggregating individual members' purchases to the household level. Under “standard” assumptions the answer is unambiguous: the household brand switching pattern looks more zero order than the typical individual family member's behavior. When the standard assumptions are relaxed the overall spirit of the results do not change. These conclusions give comfort to those who use brand switching data to partition product categories. Those looking for variety-seeking behavior from household data are given some cause for concern—as well as reasons for reinterpreting previous studies.