Auditing,consulting, and audit market concentration

In its recently published Green Paper, the European Commission (Audit policy: lessons from the crisis. Brussels, 2010) discusses various methods to enhance the reliability of audits and to re-establish trust in the financial market. The Commission primarily focuses on increasing auditor independence and on reducing the high level of audit market concentration. Based on a model in the tradition of the circular market matching models introduced by Salop (Bell J Econ 10(1):141–156, 1979), we show that prohibiting non-audit services as a measure intended to improve auditor independence can have counter-productive secondary effects on audit market concentration. In fact, our model demonstrates that incentives for independence and the structure of the audit market are simultaneously determined. Because market shares are endogenous in our model, it is not even clear that prohibiting non-audit services indeed increases an auditor’s incentive to remain independent.