Explore which audit firms audit the world’s largest listed companies, how long they have held those engagements, and how much companies pay for audit services.
The Big Four — Deloitte, PwC, EY and KPMG — dominate the audits of the world’s largest listed companies. But their market shares vary considerably between countries, industries and stock-market indices.
Who Audits? examines which firms audit major listed companies, how long those relationships have lasted, and what companies disclose about the fees they pay.
Big4News draws on company annual reports, regulatory filings and other primary sources to bring together company-level data that companies and regulators often publish in separate documents.
The research covers leading stock-market indices around the world, allowing readers to examine audit-market concentration, competition, auditor tenure and the distribution of major corporate audit engagements.
For details of the research approach, see Who Audits? Sources & Methodology.
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The global audit market at a glance
The Big Four dominate the audits of the world’s largest listed companies, but their market shares differ sharply between countries.
In the United States, the four networks audit 494 of the 500 companies in the S&P 500, representing 98.8% of the index. EY leads with 154 appointments, followed by PwC, Deloitte and KPMG. Firms outside the Big Four audit just six companies.
The FTSE 100 shows similar concentration. The Big Four audit 96 of its 100 constituents, with Deloitte, PwC and KPMG separated by only a few appointments.
Other markets tell a different story.
In Malaysia’s FTSE Bursa Malaysia KLCI, the Big Four hold 23 of 30 appointments (76.7%). BDO matches KPMG with five appointments, while Deloitte audits none of the index’s constituents.
France’s CAC 40 illustrates how joint audits change the competitive landscape. Its 40 companies have 74 statutory-auditor appointments, of which the Big Four hold 59 (79.7%). Forvis Mazars holds 13 appointments, matching KPMG. Thirty-four of the 40 companies appoint two statutory auditors.
In India’s Nifty 50, at least one Big Four network audits 36 of the 50 companies (72%). Domestic and mid-tier firms retain a significant presence, while joint-audit arrangements make comparisons based solely on appointment numbers more complicated.
These figures reveal differences between major stock-market indices, rather than measuring each country’s entire audit market. The datasets also cover different reporting dates, and comparisons must distinguish the number of companies that firms audit from the number of statutory-auditor appointments they hold.
Audit appointments do not tell the whole story
The firm with the most listed-company audit appointments does not necessarily earn the most in audit fees.
Engagement size, company complexity, international operations, regulatory requirements and financial-disclosure practices all influence audit fees.
Auditor tenure adds another dimension. Some US and Japanese companies have retained the same audit networks, including their predecessor firms, for generations. In jurisdictions that require mandatory audit-firm rotation, companies must change auditors more frequently.
These differences matter when assessing audit-market concentration and competition. Client numbers, audit-fee income and the duration of auditor relationships each offer a different perspective on the position of individual firms.
The individual market pages explore these questions through company-level datasets, audit market-share analysis, auditor tenure, recorded audit fees and the regulatory frameworks that shape each market.
What the data includes
The Who Audits? datasets typically contain four principal fields:
Company: Identifies the company within the relevant stock-market index or research group.
Auditor: Names the external audit firm or firms responsible for the statutory audit.
Since: Records the first financial year that the current firm audited, where reliable evidence establishes that date.
Audit fee: Shows the latest publicly disclosed amount for audit services, subject to the definitions and limitations of the company’s disclosure.
Some datasets also include additional fields to explain joint audits, auditor changes or company-specific reporting circumstances.
Big4News compiles the datasets primarily from annual reports, regulatory filings, independent auditor reports, shareholder documents and other primary corporate disclosures.
For each index, the research identifies auditor appointments at a specified snapshot date. It records auditor tenure when the available evidence reliably establishes the first audited financial year. It includes audit fees when published disclosures support the figures and explains relevant differences in reporting periods, joint audits, predecessor auditors and fee definitions.
Big4News does not estimate missing information. Where the research cannot establish a sufficiently reliable figure, the dataset leaves the field blank rather than recording zero.
Readers should also exercise caution when comparing audit fees between companies or jurisdictions. Reporting requirements, currencies, financial years and the scope of audit services vary. Recorded fees do not necessarily represent an audit network’s total revenue from companies in an index.
For full definitions, sourcing standards and explanations of how the research treats auditor tenure, joint audits, currency conversion, firm changes and incomplete disclosures, see Who Audits? Sources & Methodology.
Research updates
Each index page identifies its data snapshot date and, where applicable, the most recent research verification date. The datasets provide historical snapshots rather than continuously tracking auditor appointments.
Big4News follows a quarterly editorial review cycle, with scheduled reviews in mid-January, mid-April, mid-July and mid-September. Significant auditor changes, index reshuffles or corrections may also prompt earlier updates.
Readers should consult the individual index pages for the relevant reporting dates, methodology and qualifications.
Why this research matters
The identity of a company’s auditor forms an important part of its corporate governance framework. External auditors examine financial statements and express independent opinions on whether they comply with the relevant financial reporting framework, helping investors and other stakeholders assess the reliability of corporate reporting.
Yet finding information about the structure of the audit market often requires searching multiple company reports and regulatory filings.
Identifying which firms hold the largest engagements, where alternative providers have gained a foothold and how long companies retain their auditors can inform discussions about competition, independence and accountability.
Who Audits? brings these records together in one place, giving investors, researchers, journalists, regulators and other readers a clearer view of the global audit profession.
Big4News will continue to expand and update the research as new company disclosures emerge and further market analyses become available.