Analysis of Sales Promotion Effects on Household Purchase Behavior

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In general, the average quantity during the pre-promotional shopping trips (QB) does
not differ significantly from the average non-promotional purchase quantity. Households do
seem to buy somewhat less potato chips and pasta on pre-promotional shopping trips.
As expected, promotional quantity (QP) is positive for all product categories
indicating that people buy more when a product is on promotion. In general, households do
not compensate for this by purchasing less during the next shopping trip (QA is not
significantly negative except for potato chips). It is even significantly positive for two <strong>of</strong> the
six product categories (fruit juice and c<strong>of</strong>fee). With respect to c<strong>of</strong>fee, the post-promotional
shopping trip is postponed such that the net effect <strong>of</strong> purchase timing and purchase quantity
combined (CE) is not significant. But, although the subsequent fruit juice purchase moment is
postponed, a positive net effect on consumption is found (CE). In general, the promotional
quantity effect is so large that it outweighs any negative pre- and post-promotional effects,
leading to a positive net effect on purchase quantity (QN).
In general, consumers seem to be systematic shoppers. When they buy more due to
promotions (QP significantly positive), they do not buy it sooner (significant negative TA).
Purchase timing (TA) and purchase quantity (QP) seem to be two interdependent
mechanisms. The counterintuitive findings regarding the average sizes <strong>of</strong> the postpromotional
quantity effects for c<strong>of</strong>fee and fruit juice can be explained by taking this
interrelatedness between purchase time and quantity into account. Households buy more
c<strong>of</strong>fee when there is a promotion. After doing so, they postpone the next c<strong>of</strong>fee purchase
(large positive TR), probably until they reach their normal storage level. With respect to fruit
juice, category expansion (CE) effects are found. <strong>Promotion</strong>s for these products lead to extra
purchased quantities without purchase time compensation (or post-promotional quantity
decreases). Fruit juice promotions apparently lead to increased usage rates. The results
underline the importance <strong>of</strong> distinguishing the intertemporal effects <strong>of</strong> sales promotions and
the intertwining effects <strong>of</strong> purchase quantity and purchase timing. This net category effect
(CE) <strong>of</strong> sales promotions takes the interrelatedness between timing and quantity into account.