The interdependence between market structure and the quality of audited reports: the case of non-audit services

This paper addresses the effects of a prohibition of providing non-audit services (NAS) to audit clients. By combining a strategic auditor-client game with a circular market-matching model that has an endogenous number of auditors, we take into account the interdependence between the auditors' and clients' incentives, the market structure, and the quality of audited reports. We show that the regulation's effects depend on the preexisting audit market concentration and the types of blacklisted NAS. In sharp contrast to the effects that regulators desire, a prohibition of providing NAS to audit clients can further increase audit market concentration and decrease the quality of audited reports if the fees that auditors previously earned from providing the blacklisted NAS were relatively high, compared to the reduction in audit costs that result from spillovers. In contrast, a prohibition of the NAS that generate intense spillovers and low NAS fees can have the unexpected-but desired-effect of decreasing market concentration; however, reporting quality also decreases.