Abstract
We draw on industrial-organization economics theory, density-dependent and resource-partitioning theories, and brand-leveraging theories to propose a product-evel theory of market entry. The result is a more fully informed account of the relationship between the firm and its ability to shape its market environment. Our core thesis is that the relationship between product proliferation and new product entry is an inverted U, which itself is moderated by the extent of brand name sharing among incumbent products.