Analysis of Sales Promotion Effects on Household Purchase Behavior

more persons living together and dining at home at least four times a week. The sample is a
stratified sample, using ‘size <strong>of</strong> the household’, and ‘age <strong>of</strong> the housewife/househusband’
as stratification variables, applying a Neyman-allocation (drawing relatively more/less
households from strata with large/small dispersion regarding the stratification variables
(Luijten 1993). Because <strong>of</strong> non-response (caused by all kinds <strong>of</strong> reasons, such as vacation,
illness, and real non-response), social class, size <strong>of</strong> the municipality, and district are used as
weights within each stratum. Appendix A6 provides an overview <strong>of</strong> the variables involved
in the sample procedure.
Although household panel data <strong>of</strong>fers several important advantages over store
level data, it is <strong>of</strong>ten feared that this data is not representative. Russel and Kamakura
(1994) did not find evidence that household panel data is nonrepresentative <strong>of</strong> store data.
Tellis and Zufryden (1995) and Gupta et al. (1996) demonstrated that panel data provides
unbiased estimators for general behavioral indicators, but more specific estimators are
biased. Luijten and Hulsebos (1997) investigated the representativeness <strong>of</strong> the GfK
ConsumerScan panel <strong>of</strong> the Dutch population. They concluded that the panel members are
as price sensitive as non-panel members, and have the same attitudes towards media
behavior, store choice, and store evaluation. Price knowledge differs for some product
categories, where, in those cases, panel members were better informed about the exact
prices. Panel members also turned out to have more interest in leaflets, brochures, etc.
Most households in the dataset are not single-person households (81.2%), which
could lead to the problem that purchases from the same household may reflect the choices
<strong>of</strong> different consumers on different purchase occasions (Mayhew and Winer, 1992). If the
shopper within the household changes from one purchase occasion to the next, a possible
brand switch does not have to be caused by, for example, promotional activity or variety
seeking behavior at the individual consumer level. Conclusions are therefore drawn at the
household level, not at the individual consumer level. For each <strong>of</strong> these 4060 households,
we have information available for the six product categories mentioned above. More
specifically, we have information on the specific item bought, the retail chain, the amount
bought, the price paid, and the day and time <strong>of</strong> the purchase (morning, afternoon, or
evening).
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