During that same period, direct marketers and catalogers began to develop very sophisticated approaches using regression, CHAID, CART, and other statistical techniques. There, the focus was almost entirely on observable consumer behaviors in the form of longitudinal purchase occasions. This was followed by Jones and Sasser's (1995) and Reichheld's (1996) seminal articles on the economic value of customer loyalty in the 1990s. Reichheld's text "The Loyalty Effect" (1996) has set the direction and tone for much of the loyalty thinking over the past several years.