Let a large-number of small-individuals contribute to charity. We show that ‘strong aggregate complementarity’ is necessary for multiple equilibria in a competitive equilibrium. Consider two equilibria with low (L) and high (H) levels of giving. Suppose that society is stuck at L and wishes...

Consider a large number of small individuals contributing to a charity or to a public good. We study the properties of a competitive equilibrium in giving and allow for multiple equilibria. Our proposed condition, aggregate strategic complementarity, is a necessary condition for multiple...

In a competitive-equilibrium analysis of giving to charity, we show that strategic complementarity between individual giving and aggregate giving can lead to multiple equilibria. This provides a possible explanation for observed heterogeneity in giving. It is possible, but not necessary, that at...