Untangling the Effects of Purchase Reinforcement and Advertising Carryover

The dynamic evolvement of market share of a brand in a frequently purchased product category can be driven by two effects, purchase reinforcement, and advertising carryover. The first depends on the actual experience with the brand while the second on the retention of its producer's messages. We present a model to estimate simultaneously the relative magnitude of these two forces. The model also formally treats the issue of temporal aggregation. Our empirical results with several product categories indicate that for monthly and bi-monthly measurement periods, purchase reinforcement dominates carryover of advertising in affecting the evolution of market share.