Auditor Market Share of the Russell 3000

It is no secret that the Big Four auditors – Deloitte, EY, KPMG and PwC –  dominate at the top of the public company audit market. Large companies almost exclusively use the Big Four, while a handful of other firms compete for the remaining share.

In a previous analysis, we looked at auditor market share of Russell 3000 companies with revenues between $50 million and $1 billion. In this post, we look at the auditor market share of all Russell 3000 companies for fiscal year 2018.

To illustrate, we broke the Russell 3000 into quartiles based on fiscal 2018 revenue.

  • 1st Quartile: $0- $245 million
  • 2nd Quartile: $245 million – $900 million
  • 3rd Quartile: $900 million – $3,145 million
  • 4th Quartile: more than $3,145 million

The percentage of companies that are audited by Big Four vs. non-Big Four firms are presented in the following chart:

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Looking at companies with revenues up to $245 million, 62 non Big-Four firms compete for 48% of this quartile (or 362 companies).

When focusing on companies in the second quartile, with revenue between $245 million and $900 million, 24 non-Big Four firms audit 26% (or 196 companies). In the third quartile, there are only nine non-Big Four firms that audit 10% of this revenue range (or 73 companies).

In terms of market share across all quartiles, there are only two audit firms other than the Big Four that audit more than 100 companies in the Russell 3000: Grant Thornton and BDO USA. Crowe and RSM each have over 60 audit clients.

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There are 31 audit firms that audit only one company in the Russell 3000.

For more information on this analysis please contact us at or (508) 476-7007.