Mystery shoppers focus on the behaviours they have been sent to inspect for. Because these behaviours bear no relation to the variety of customer demands they can cause sub-optimisation through wasting time, saying things to customers that customers have no interest in hearing and spoiling the relationship with customers. That can only lead to further losses.

A further form of sub-optimisation is the impact this kind of inspection has on morale. When the only joy you have at work is spotting mystery shoppers…