Customer loyalty programs aim to increase sales revenues and products purchased by building closer bonds between brands and customers. There are three popular models of customer loyalty: monogamy based on attitudinal loyalty, polygamy based on past purchase behavior, and promiscuity based on individual characteristics and circumstances. The implications of these models differ, with attitudinal loyalty programs focusing on enhancing positive beliefs and emotional commitment, behavior-based programs matching competitors, and contingency-based programs responding to situational factors. Loyalty programs are aimed at both increasing individual single-brand loyalty and growing brand size in the market through combination with other marketing efforts.