Product Proliferation: An Empirical Analysis of Product Line Determinants and Market Outcomes

Abstract

Previous theoretical research has identified three primary effects of a product proliferation strategy: (1) a broad product line can increase overall demand, (2) a broad product line can affect supply by increasing costs, and (3) broad product lines can have strategic consequences (e.g., long product lines can deter entry, thereby allowing an incumbent firm to raise prices). In this paper we propose a three-equation simultaneous system that captures both the determinants and market outcomes of a firm's product line decisions. In particular, we specify market share, price and product line length equations, which are estimated by three stage least squares. Our empirical results for the personal computer industry over the period 1981-1992 demonstrate that product proliferation decisions have both demand (market share) and supply (price) implications. Our empirical results also suggest that the firm-level net market share impact of product proliferation in the personal computer industry is negative (i.e., the cost increases associated with a broader product line dominate any potential demand increases). As expected, we find that structural competitive factors play an important role in the determinants and market outcomes of a firm's product line decisions. However, we do not find evidence of firms using proliferation strategies to deter entry in this industry. Finally, we also demonstrate that some of the empirical conclusions from previous research are reversed once product line length is specified as endogenous in the share and price specifications.