In this paper we study the effect of downward social information in contribution decisions to fund public goods. We describe the results of a field experiment run in conjunction with the fundraising campaigns of a public radio station. Renewing members are presented with social information (information about another donor's contribution) which is either above or below their previous (last year's) contribution. We find that respondents change their contribution in the direction of the social information; increasing their contribution when the social information is above their previous contribution, and decreasing their contribution when the social information is below. We hypothesize about the psychological motivations that may cause the results and test these hypotheses by comparing the relative size of the upward and downward shifts. These results improve our understanding of cooperation in public good provision and suggest differential costs and benefits to fundraisers in providing social information.