We analyze demand for prepaid cellular voice and short message service (SMS) in South Africa by means of a demand-and-supply structural model based on a multinomial specification fitted to a cross-sectional data set on Vodacom customers collected in 2005. We find that consumers are very...

We propose a theory of supervision with endogenous transaction costs. A principle delegates part of his authority to a supervisor who can acquire soft information about an agent's productivity. If the supervisor were risk-neutral, the principal would simply make the better informed supervisor...