8fcb62ec_rics___Introduction___FT_Press__Considerations
[0] 2.4 2.5 2.6 [Metric] Decomposition of Market Share [Construction] Penetration Share * Share of Requirements * Heavy Usage Index. [Purpose] Calculation of market share. Competitive analysis. Historical trends analysis. Formulation of marketing objectives. [Considerations] 
Can be based on unit or revenue shares. Time period covered.
Marketing Metrics: Understanding Market Share and Related Metrics | Introduction | FT Press
Considerations