Promotions and the pattern of grocery shopping time

The histograms of interpurchase times for frequently purchased packaged goods have consistently shown pronounced seven-day cycles. Evidence supports that the weekly spike phenomenon is the result of consumers' regular shopping trip schedules. We explore the implications of this peculiar regularity on the issue of consumer purchase timing acceleration. Data for five product categories are examined. Promotions are found to have little effect in accelerating purchase timing. In contrast, conventional interpurchase time models are shown to overstate the effect of promotions.