The Impact of the Big 4 Consolidation on Audit Market Share Equality

SUMMARY: We investigate the Big 5 to Big 4 consolidation and its impact on audit market share equality. We extend the GAO’s (2008) study on audit firm industry market concentration to examine whether the remaining Big N firms’ market shares are more equal after the Big 4 consolidation. We also extend the GAO study to examine audit market shares at the city and city-industry levels. We find that while overall market concentration increases, the Big 4 have more equal market shares than the Big 5 had prior to the consolidation at all levels of analysis. The increase in market share equality may explain why there has been inconsistent evidence of an association between market concentration and competition after the consolidation (Feldman 2006; GAO 2008). However, we find that the largest four clients in each market we examine are more likely to share the same auditor after consolidation, which suggests the largest clients face constrained choices.