Experimental Design
This section describes the experimental design of the three variants of the incentivized public goods game (PGG). In this study, YAIG members, including leaders, participate in the experiment. Each participant receives an initial endowment of 200 Birr and is randomly matched with three other anonymous participants from the same YAIG. At the time of the study, $1 approximately 155 Ethiopian Birr. Participants privately decide how much of the 200 Birr to keep for themselves and how much to contribute to a group account. Contributions can range from 0 to 200 Birr in increments of 20 Birr (0, 20, 40, 60, 80, 100, 120, 140, 160, 180, and 200 Birr). The amount kept directly benefits the participant. The amount contributed to the group account is doubled, but the beneficiary of the doubled contribution differs across the three treatment arms.
The experiment follows YAIG level clustered randomization. The 183 YAIGs are randomly assigned to one of three experimental arms, stratified by kebele, as there are multiple YAIGs in each kebele. All participating members and leaders within a YAIG are assigned to the same experimental arm. With each YAIG, participants are anonymously matched into four-person groups for the contribution decision.
Arm 1: Standard PGG arm
In this arm, participants are randomly paired with three other anonymous participants from the same YAIG. Each participant decides how much of the 200 Birr endowment to keep and how much to contribute to the group account. The experimenter doubles the total amount
contributed by the four matched participants and shares the doubled amount equally among them. A participant’s payoff in this arm equals the amount kept for oneself plus one-fourth of the doubled group account.
This arm is a standard, context-free PGG with a social dilemma: contributing is socially beneficial but privately costly. With four participants and a multiplier of two, each Birr contributed returns 0.5 Birr to the contributor but increases total group earnings by 2 Birr. Of the 183 YAIGs, 62 are randomly assigned to this arm.
Arm 2: YAIG contribution arm
In this arm, the contribution is framed as a contribution to the participant’s YAIG account. Participants are anonymously matched with three other participants from the same YAIG and decide how much of the 200 Birr endowment to keep and how much to contribute. The total contribution of the four matched participants is doubled and transferred to the participant’s own YAIG account. Participants directly receive only the amount they keep for themselves, while the contribution benefits the YAIG as an organization. This arm captures cooperation
directed toward an identifiable in-group institution, where benefits accrue to members of the participant’s own youth organization. Of the 183 YAIGs, 61 are randomly assigned to this arm.
In Arm 3: Forest contribution arm
In this arm, the contribution is framed as support for a local forest reserve, the Yayu Forest Coffee Biosphere Reserve. Participants are anonymously matched with three other participants from the same YAIG and decide how much of the 200 Birr endowment to keep and how much to contribute. The total contribution of the four matched participants is doubled and transferred to support conservation activities in the reserve. Participants directly receive only the amount they keep for themselves, while the contribution supports a broader environmental and social public good. This arm captures cooperation directed toward a public good that extends beyond the participant’s immediate youth organization. Of the 183 YAIGs, 60 are randomly assigned to this arm.