In this study we focus attention on Big 4 audit pricing. First, the most basic spatial location choice is that of large versus
small auditor, and hence we want to keep this location choice constant in our analysis. Second, prior studies on the fee
effects of industry specialization also focus on Big 4 audit markets (Ferguson et al., 2003; Francis et al., 2005). Third, the
theory of location economics typically applies to oligopolistic settings with only a few suppliers, which is consistent with
the Big 4 oligopoly. However, it is possible that (at least some) non-Big 4 audit firms compete with Big 4 audit firms at the
local MSA level for clients. That is, in some audit markets a non-Big 4 audit supplier could be the closest competitor of a
Big 4 audit firm. Therefore, in supplemental tests we re-run our analysis measuring Distance_competitor based on the
entire (Big 4 and non-Big 4) audit market.