OBJECTIVES: Budget impact models rely on robust estimates for market share uptake of the new therapy/intervention being introduced. The aim of this study was to evaluate the techniques informing market share uptakes in previously published budget impact models (BIMs).

METHODS: A comprehensive literature review was conducted in PubMed between 2017-2022 to identify BIMs estimating projected market shares over a one-year time horizon. Studies were assessed to identify techniques and penetration estimates used.

RESULTS: 961 studies were identified in the comprehensive search and 147 studies were included in the review. Almost half of the studies were conducted in North America (44%), followed by Europe (34%) and Asia (12%). 108 studies (73%) used assumptions without explanation to estimate their projected market shares whereas 11 studies (7%) employed expert opinion to gain their estimates. Seven studies (5%) used sponsor estimates for their projected market shares and 13 studies (9%) estimated using historical data either from market research or pharmaceutical sales data. Four studies calculated their projected market shares using statistical methods, such as approximation using a Lehman curve and using a ratio of generic products and both generic and associated patented drugs sold.

CONCLUSIONS: To our knowledge, this is the first targeted review that investigated techniques used for market share uptakes in BIMs. Most studies used the standard method of devised assumptions, expert opinion, market share research and historical data. Novel methods were also identified in several studies. Further transparency and established guidance in estimating market share uptake would be valuable in ensuring the robustness and comparability of BIMs.