Avoidable Cost: Ride a Double Auction Roller Coaster

The double auction trading institution (DA) has been highly efficient across diverse marginal-cost market structures, whether human subjects or "zero-intelligence" robots populated those markets. Accordingly, many researchers suspect that DA performance transcends market structure and agent strategy. But we show that (1) large avoidable costs undermine the efficiency and stability of human subject DAs, and (2) these low human efficiencies are simultaneously well above zero-intelligence efficiencies. Our results dramatically illustrate the potential havoc wrought by highly competitive institutions when they must cope with nonconvex technologies.