Empirical evidence of the effect of mandatory audit firm rotation on market concentration in South Africa

Background: The audit market in South Africa is dominated by the Big Four audit firms, which decreases competition and may result in reduced productivity, innovation and economic growth.Aim: This study analyses the auditor rotations from June 2017 to April 2023 to determine whether mandatory audit firm rotation (MAFR) has reduced audit market concentration by decreasing the dominance of the Big Four in favour of medium-sized audit firms.Setting: The audit regulator in South Africa has raised concerns about the dominance of the Big Four. As a response, the audit regulator implemented an MAFR ruling. While the courts have set aside the MAFR ruling, the audit regulator still plans to pursue MAFR, believing it is an effective response mechanism.Method: The study uses content analysis for inspecting the financial statements and Stock Exchange News Service announcements for audit tenure and details regarding the change of auditors for the Johannesburg Stock Exchange Top 100 companies. The proportion of entities audited by the Big Four and medium-sized audit firms is calculated from 2017 to 2023.Results: The dominance of the Big Four increased as only three out of the 57 rotations observed resulted in an entity moving from one of the Big Four to a medium-sized audit firm.Conclusion: The empirical evidence gathered shows that MAFR was ineffective in reducing market concentration.Contribution: The results and recommendations of this study are relevant for the audit regulator to consider evaluating whether it should continue to pursue MAFR as a mechanism to reduce market concentration.