Discovering association strength among brand loyalties from purchase history

Analyzing the purchase history of customers enables us to discover valuable knowledge that is helpful for developing effective sales promotion. In this respect, the authors introduce a new notion, association strength among brand loyalties, which is defined for every ordered pair of brands. If the association strength between loyalties of brands A and B is high, it represents that purchase of brand A is highly correlated to that of brand B. The conventional method for discovering associative purchasing is usually applied for one purchase opportunity (one receipt), i.e., it reveals how often two commodities are purchased at the same time. On the other hand, they are interested in discovering relationship among customers´ loyalties to certain brands or manufacturers by investigating long-term purchase history of customers. By computing association strengths from customers´ purchase history of drugstore chain in Japan, one can produce several interesting rules that will be useful for sales promotion planning