Unintended consequences of Big 4 auditor office-level industry specialisation

The Big 4 audit firms currently dominate the US audit market. We investigate whether the extent of a Big 4 local office's dependence on industry specialist clients impacts audit effort/earnings quality for the office's specialist as well as non-specialist clients. Our findings suggest that greater dependence on specialist clients is associated with higher audit effort/earnings quality for specialist clients but also with lower audit effort/earnings quality for the office's non-specialist clients. Our results hold when we propensity-match specialist and non-specialist clients to control for client characteristics as a possible confounding explanation. Our study is important, because it: 1) contributes to prior research that is largely silent on whether cross-sectional variations in reputation for industry-expertise are associated with variations in audit quality (DeFond and Zhang, 2014); 2) suggests that, it would be appropriate for PCAOB inspectors to focus on non-specialist clients at audit offices with greater dependence on specialist clients as an area representing higher risk of lower audit effort/quality.