- Market share plays a central role in a number of portfolio planning models. This article presents an exposition of the underlying relationship between market share, market size, market growth rate, product sales volume and product sales growth rate. Three constructs-the market share multiplier, the physical volume multiplier, and the dollar volume multiplier-which aid in the strategic analysis of the product portfolio are proposed. The linkages between inter-related growth constructs such as the volumetric and dollar sales growth rate, and the nominal and real dollar sales growth rate are discussed. Certain generalizations regarding market share and its sensitivity to various environmental conditions are highlighted. 1990 Academy of Marketing Science.