Horizontal (vertical) elasticities of price transmission in a competitive market can be positive or negative in sign depending on whether observed changes in market prices are triggered by shifts in the supply or demand for the commodity or by changes in trade (marketing) costs. These facts suggest estimates of horizontal (vertical) elasticities of price transmission obtained from empirical models that exclude trade (marketing) costs will suffer from attenuation bias. The attenuation bias is apt to cause inferences about market efficiency to be more pessimistic than is warranted.

中文翻译：

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横向和纵向价格传导对应关系的一个注解

竞争市场中价格传导的水平（垂直）弹性可以是正数或负数，这取决于观察到的市场价格变化是由商品供需变化还是由贸易（营销）成本变化引发的。这些事实表明，从排除贸易（营销）成本的经验模型中获得的价格传导水平（垂直）弹性的估计值将受到衰减偏差的影响。衰减偏差容易导致对市场效率的推断过于悲观。