City markets as a unit of analysis in audit research and the re-examination of big 6 market shares

Big 6 market shares based on aggregate national data have been used in prior research to infer market leadership and industry expertise, and to differentiate Big 6 accounting firms from one another. In this study it is demonstrated that further differences exist with respect to city-specific audit markets, both between firms and within the same firm across different city markets. The specific finding is that the national market leader is not the city-specific market leader the vast majority of time. Usefulness of the city-level unit of analysis is further demonstrated by re-examining the 1989 mergers creating Ernst & Young and Deloitte Touche. The primary effect of the Ernst & Young merger was to increase market shares in cities in which the pre-merger firms already had significant market shares, resulting in an increase in the number of cities in which the merged firm achieved top ranking. In contrast, the primary effect of the Deloitte Touche merger was an expansionof the number of city-level markets in which the merged firm had significant (though not leading) market shares. The findings of this study suggest that, in order to move beyond our current understanding, important audit research questions such as the reason for particular auditor–client alignments, the competitive nature of markets, audit pricing of reputations, and auditor reporting and independence issues should be investigated in city-level markets where audit contracting occurs and where Big 6 market shares (and presumably reputations) vary widely from city to city.