A Review of the Literature on Joint Audit and Its Effects on Audit Quality, Audit Costs, and Market Concentration

This study reviews the literature on joint audits published between 2014 and 2024, focusing on their effects on audit quality, audit costs, and audit market concentration. A systematic search of ProQuest, Google Scholar, Scopus, and ScienceDirect identified 37 relevant studies. Of these, 16 (43.2%) examine developed markets, while 21 (56.8%) focus on developing economies, particularly Arab countries. The evidence on audit quality remains inconclusive. Sixteen studies (43.3%) report that joint audits improve audit quality, twelve (32.4%) find negative effects, and nine (24.3%) present mixed or insignificant results, indicating continued empirical disagreement. Early European studies, which primarily rely on accrual-based measures and audit fees, generally report neutral or negative outcomes. In contrast, more recent studies using broader proxies such as earnings management, accounting conservatism, and perception-based measures tend to show more positive effects, especially in emerging economies. Regarding audit costs, most studies suggest that joint audits increase audit fees, although results vary across institutional contexts. Evidence on the role of joint audits in reducing audit market concentration remains limited and inconclusive. Overall, the review highlights significant institutional, geographic, and methodological gaps. The effectiveness of joint audits appears highly context-dependent, influenced by regulatory environments, cultural factors, and auditor composition.