Validity of Auditor Industry Specialization Measures

Over the years, researchers have developed several measures of auditor industry specialization (ISP). However, there is not much information regarding the characteristics of each of these measures, as well as the sensitivity of previous research results to these ISPs. In this research, using the data of 211 firms listed in the Tehran Stock Exchange, during the years 1389 to 1400 (including 2,242 firm-year observations), 25 different measures of ISP was calculated and their internal and external construct validity was investigated. The results show that the use of different measures of ISP leads to the inconsistent classifications of auditors as specialists. Furthermore ,the use of the discretionary accruals quality model for the external validity test for measures of ISP shows that the inconsistency between the measures of ISP has a significant impact on the inferences regarding the impact of auditor expertise on earnings quality. In this way, the results of the current study show a low degree of internal and external validity of various constructs of auditor industry expertise and raise some questions about the stability of previous empirical evidence on auditor industry specialization.