We find that over six hundred auditors with fewer than 100 SEC clients exit the market following SOX. Compared to the non-exiting auditors, the exiting auditors are lower quality, where quality is gauged by: (1) avoidance of AICPA peer reviews and failure to comply with PCAOB rules, and (2) severity of the peer review and inspection reports. In addition, clients of exiting auditors receive higher quality auditing from successor auditors, as captured by a greater likelihood of receiving going concern opinions. Our results suggest that the PCAOB inspections improve audit quality by incentivizing low quality auditors to exit the market.

Exploiting a natural experiment in which voluntary audits replace mandatory audits for U.K. private companies, we analyze whether imposing audits suppresses valuable information about the types of companies that would voluntarily choose to be audited. We control for the assurance benefits of auditing to isolate the role signaling plays by focusing on companies that are audited under both regimes. These companies experience no change in audit assurance, although they can now reveal for the first time their desire to be audited. We find that these companies attract upgrades to their credit ratings because they send a positive signal by submitting to an audit when this is no longer legally required. In contrast, companies that dispense with being audited suffer downgrades to their ratings because avoiding an audit sends a negative signal and removes its assurance value. Data Availability: All data are available from public sources.