Vertical line extension: a systematic review of research on upward and downward line extension

Purpose Vertical line extension is an attractive growth strategy that allows brands to address heterogeneous consumer needs and react to competitive pressure. The purpose of this paper is to systematically review and summarize vertical line extension research to derive general insights into vertical upward and downward line extension. Design/methodology/approach Drawing on a systematic review of 536 academic articles and predefined inclusion criteria, this research identifies and evaluates all articles that add knowledge to the topic of vertical line extension (n = 64). Findings This research derives general insights in several vertical line extension-specific issues. Different forms of vertical line extension, conceptual differences between upward and downward extensions, as well as the role of perceived fit, extension degree and the parent brand are crucial for the study and evaluation of extension and parent brand feedback effects. Those effects are complex and often work in opposing directions not only for the parent brand but also for the extension. Future research needs to face that complexity as well as methodological issues and different research contexts to further advance the literature stream. Originality/value This paper provides a comprehensive, state-of-the-art review of vertical line extension research characteristics and results. It provides new insights on the characteristics and effects of vertical line extensions and guides future research on the topic.