There are three different treatment conditions, henceforth referred to as Time, Money and the control group. All apprentices receive a personal letter sent to their home address from the firm’s HR office. For apprentices in the control group, essentially nothing changes during the treatment. They are only made aware of a project called “Attendance Bonus” and that this project will be relevant to them at some later stage. Apprentices in the remaining two treatment groups are notified that they receive a “bonus point” for each month without a single day of absence due to sickness. The total duration of the experiment is twelve months. After every three months in the treatment period, the incentivized apprentices receive feedback on their current point score. However, bonus points are only transformed into actual rewards after the end of the experiment. Importantly, only the total number of accumulated points is payoff-relevant. The reward function is identical for both the Money and the Time condition. However, the two treatments differ with respect to the nature of the employed reward domain.
In the Time treatment, one reward unit corresponds to an extra holiday. A maximum number of four extra holidays can be achieved. The respective apprentices are granted their extra holidays two months after the end of the treatment period. From then on, the apprentice is free to choose when to make use of the additional holidays. Only store type I apprentices are eligible for the Time treatment for administrative reasons.
In the Money treatment, one reward unit corresponds to a bonus payment of €60. That is, a maximum bonus payment of €240 can be achieved. This conversion rate is chosen such that the values of a single reward unit are approximately equivalent for both reward domains. The respective apprentices receive their bonus payments in addition to their regular salary two months after the end of the treatment period.
Apprentices in the control group are not incentivized. Yet, they receive a notification prior to the beginning of the treatment period vaguely indicating that randomly chosen groups of apprentices will receive some sort of attendance contingent reward. Furthermore, they are notified that they will receive a comparable reward at a later point in time. In the context of the retail chain, informing the control group is inevitable, since apprentices in different treatment groups may yet attend the same vocational training school and thus exchange information. Therefore, informing those apprentices who are not incentivized that they are not systematically disadvantaged may prevent them from alternating their (attendance) behavior as an act of defiance.