Assume that two companies, A and B, are competing against each other for the market share in a local region. Let x and y be the market share of A and B, respectively. Assuming that there are no other third-party competitors, x + y = 1 (100%), and therefore this system can be understood as a one-variable system. The growth/decay of A's market share can thus be modeled as dz d.r = ax(1-x)(a-y), (1 -x (x-y) (8.18) where ar is the current market share of A, 1 - r is the size of the available potential customer base, and - y is the relative competitive edge of A, which can be