Investigating consumers' purchase incidence and brand choice decsions across multiple product categories: A theoretical and empirical analysis

We propose a framework to investigate consumers' brand choice and purchase incidence decisions across multiple categories, where both decisions are modeled as an outcome of a consumer's basket Utility maximization. We build the model from first principles by theoretically explicating a general model of basket utility maximization and then examining the reasonable restrictions that can be placed to make the solution tractable without sacrificing its flexibility. Comparing with prior models, we show why prior multicategory purchase incidence models overemphasize the role of the cross effects of a market mix of brands in other categories on the purchase incidence decision of a given category. Additionally, we show that prior singlecategory models are a special case of the proposed model when further restrictions are placed on the basket utility structure. We estimate the model on household basket data for the laundry family of categories. We show (i) why prior single-category and multicategory models would systematically bias the estimates of the own- and cross-price/promotional purchase incidence elasticities; and (ii) how the market mix of each brand in each category affects the purchases across all categories, which can help retailers make promotional decisions across a portfolio of products.