Policy-makers world-wide have proposed a new contract – the “social impact bond” (SIB) – which they claim can allay the underperformance and underfunding afflicting not-for-profit sectors, by tying the private returns of (social) investors to the success of social programs (Bolton 2010;...

We look at imperfectly competitive markets where some consumers might be budget-constrained. We find that the equilibrium price under budget constrained demand (say, pB ) is often higher than the equilibrium price under standard demand (say, pA ). The relationship between pB and pA depends on...