When alternative market institutions are available, traders have to decide both where and how much to trade. We conducted an experiment where traders decided first whether to trade in an (efficient) double-auction institution or in a posted-offers one (favoring sellers), and second how much to trade. When sellers face decreasing returns to scale (increasing production costs), fast coordination on the double-auction occurs, with the posted-offers institution becoming inactive. In contrast, under constant returns to scale, both institutions remain active and coordination is slower. The reason is that sellers trade off higher efficiency in a market with dwindling profits for biased-up profits in a market with vanishing customers. Hence, efficiency alone might not be sufficient to guarantee coordination on a single market institution if the surplus distribution is asymmetric. Trading behavior approaches equilibrium predictions (market clearing) within each institution, but switching behavior across institutions is explained by simple rules of thumb, with buyers chasing low prices and sellers considering both prices and trader ratios.

当有其他市场机构可用时，交易者必须决定在何处交易以及要交易多少。我们进行了一个实验，交易者首先决定是在（高效）双重拍卖机构中进行交易，还是在已发行报价的机构中（有利于卖方）进行交易，其次决定进行多少交易。当卖方面临规模收益减少（生产成本增加）的情况时，就会发生双重拍卖的快速协调，而报价机构则变得不活跃。相反，在规模报酬不变的情况下，两个机构都保持活跃，协调速度变慢。原因是卖方在利润减少的市场上以更高的效率为代价，而在客户流失的市场上以偏高的利润为代价。因此，如果盈余分配不对称，仅靠效率可能不足以保证在单一市场机构上的协调。交易行为接近每个机构内的均衡预测（市场清算），但是通过简单的经验法则可以解释跨机构的行为，买主追逐低价，卖主同时考虑价格和交易者比率。