Variability and the Duration of Search
研究报价分布变异性如何影响搜寻持续时间，发现变异性对搜寻时长的影响取决于搜寻成本的正负，统一了以往文献中的矛盾结论。
In sequential search models the variability of the offer distribution affects the duration of search in different ways. To agents searching for the highest offer, increased variability raises the reservation value (as shown in Kohn and Shavell 1974) which raises the expected duration of search; increased variability, however, also raises the likelihood that extreme offer values are observed which lowers the expected duration of search. Previous studies have examined the net effect of variability on the expected duration of search for specific cases. Venezia (1980) demonstrates that changes in variability have no net effect on the expected duration of search, but this result is shown for a normal distribution in the context of a finite horizon search model without recall and without search costs or discounting. Lippman and McCall (1986), on the other hand, proves that increases in variability raise the expected duration of search in an infinite horizon context with discounting. This paper uses a standard search model without learning about the offer distribution that encompasses the models of the above authors. It shows how their specific results follow from the one more general principle which establishes that a proportionate mean preserving spread of the offer distribution will raise, not change, or lower the expected duration of search depending on whether the sum of implicit and explicit search costs is positive, zero, or negative.