Auditor Specialization in the Industry and Audit Market Structure

The market structure shows the organizational characteristics of the market that is identified by the nature of competition and pricing in the market. The results of previous researches show the effects of the structure of the audit market on audit fees, audit quality, and competition in this market. Although this issue confirms the Structure-Conduct-Performance approach, according to the Chicago U.C.L.A. school, market performance affects market behavior and then market structure. Due to the importance of understanding the structure of the audit market and knowing how the market determines the fee and quality of auditing, identifying the factors affecting these two variables in the audit market is very important. Auditor specialization is one of the factors that affect the delegation of work to audit firms and the structure of the audit market. This issue increases the auditor market share in a particular industry because customers ask for the specialized services of auditors. The purpose of this research is to investigate the relationship between auditor specialization and audit market structure for the firms listed in the Tehran Stock Exchange (TSE) during 2007-2018.  

Audit market structure was computed by concentration indexes, including concentration ratio, Herfindahl-Hirschman index, and Entropy Index. The total market shares of three auditing firms, the members of the Iranian Association of Certified Public Accountants with the highest market share per year, were used to calculate the concentration ratio. The market share approach was used for calculating auditor specialization. Data were collected for analysis using the Rahavard databases, the Codal site, and explanatory notes to the financial statements. For robustness tests, all three indices of the audit market structure including concentration ratio, Herfindahl-Hirschman index, and entropy index were calculated based on client sales. A Panel data model was used to test the research hypotheses.  

Results showed that auditor specialization has a direct and significant relationship with three audit market indices of concentration ratio, Herfindahl-Hirschman index, and Entropy Index. With an increase (decrease) in the specialization of the audit firm industry, the audit market concentration increases (decreases). Similarly, control variables, which included client size and concentration, has a direct and significant relationship with audit market concentration. The results of robustness tests showed that if the audit market concentration indicators are calculated based on the sales of the client, the research findings are robust.  

Auditor specialization arisen from auditor behavior is an important factor in the distribution of the market among audit firms and audit market concentration, which is consistent with Chicago U.C.L.A. School. Therefore, audit firms are encouraged to increase their specialization in a particular industry so they can gain more market share in the long run.