Economic Theory Seminar Series: Middlemen: the good, the bad, and the ugly

This paper examines the role of a middleman as an expert in markets with asymmetric information. A seller has one unit of an indivisible good whose quality is determined by his effort. Buyers observe neither the seller's effort nor the quality of the good. A middleman, after observing a signal about the quality of the good, decides whether to purchase it and then to sell it to buyers. We show that the presence of a middleman may either reduce or exacerbate the seller's moral hazard problem. We also consider the model with multiple middlemen. We find that the seller's effort is minimized if either the middleman's signal is perfect or the number of middlemen is large.