The efficiency of decentralized and centralized markets for lemons

In markets with adverse selection, when average quality is low and frictions are small decentralized trade produces a greater surplus than predicted by the competitive model: under decentralized trade some high-quality units of the good trade whereas, due to the "lemons problem", only low-quality units trade in the competitive equilibrium. This suggests a reason why these markets are often decentralized. Remarkably, under some conditions payoffs are competitive as frictions vanish, even though all qualities trade