'Expressive' obligations in public good games: Crowding-in and crowding-out effects

We study individual contributions in a repeated linear public good experiment in which, in each period, subjects are required to contribute a minimum amount and face a certain probability of being audited. Audited subjects who contribute less than the required amount are convicted to pay the difference between the obligation and the voluntary contribution. We investigate the 'expressive' force of the obligations. While at early stages subjects contribute the minimum level, with repetition contributions decline below the required amount. We observe that expressive obligations exert a rather robust crowding-out effect on voluntary contributions as compared to a linear public good game. Crowding-out is stronger when payments collected through the auditing procedure are distributed to subjects rather than when they are a deadweight loss.