Coupons are increasingly gaining importance as a sales promotion tool in German retail. They are particularly suitable for short-term sales boosts. However, the long-term effects of coupon usage remain largely unclear. Thomas Kaiser therefore investigates the long-term sales impact of coupon promotions to determine what long-term effects coupon usage has and to what extent consumer-specific characteristics of coupon redeemers can influence this relationship. The author develops a panel econometric sales response model, which is empirically examined using real transaction data from a retail company's loyalty program, in order to gain new insights into coupons and their determinants of effectiveness for promotion research and practice.