Cross-buying in the digital world

How to increase cross-buying in the digital world? That is the overall research question of this dissertation. The discovery and exploration of the "(in)completeness effect" stands at the core of this research work. This effect is based on a transfer of insights from research in psychology on the „urge to complete“ of human beings to consumer behavior. Psychologists have identified a fundamental urge to complete a task once you have started it. An incomplete task creates a state of tension which can only be removed by reaching the goal of completion. Through the marketing of unused products or product categories as still-missing parts of an already used product program aiming to be completed, these insights from the psychological research can be used to increase cross-buying. We could demonstrate this by conducting field and laboratory experiments with banking and winery products. We have used jigsaw puzzles or product configurators designed in analogy to (Panini) sticker albums to visualize the completion goal and the (temporary) incompleteness of product programs very intuitively. As a consequence, customers had an increased interest in the unused product categories and the share of customers buying the complete set of offered products was many times higher than in conventional forms of marketing. We could also determine the mediators for the "(in)completeness effect" and additional completion effects for more cross-buying which are in accordance with the completion theory of psychology: Consumers feel an impulse to complete the product program and a state of tension in case of (temporary) incompleteness. The furthermore identified moderators of the "(in)completeness effect" are also in line with the underlying theory and very helpful for the right design of holistic product programs to profit from this completion effect in the best way. At the end of the dissertation a product program design is outlined that includes all insights of this dissertation as best practice to increase cross-buying in the digital world.