How Deloitte, KPMG, EY, and PwC Built a $220 Billion Empire
The Big 4 didn't just show up one day. Deloitte, KPMG, EY, and PwC are the result of nearly two centuries of expansion, aggressive mergers, and one very dramatic scandal that wiped out their only serious competitor. Understanding how they got here isn't just a history lesson — it explains why they still dominate every major audit contract on earth.
The Big 4 combined generate over $220 billion in annual revenue and employ more than 1.5 million people worldwide — a market position built over 180 years of consolidation, not overnight success.
Here's the full story, from Victorian-era ledger books to the oligopoly you're trying to break into today.
Scotland Invented Modern Accounting (Yes, Really)
Before the 19th century, bookkeeping existed — but there was no formal profession, no certification, and no standards. The Industrial Revolution changed that fast. As factories scaled up, joint-stock companies multiplied, and railways started connecting continents, investors needed someone to verify the numbers they were being shown. That demand created the modern accountant.
Deloitte — William Welch Deloitte opened his London practice in 1845, making it the oldest predecessor firm still bearing its founder's name. He was among the first to be appointed an independent auditor to a railway company — then the hottest sector in the world.
KPMG — Traces its roots to multiple 19th-century firms across the UK, Netherlands, and US, including Peat Marwick Mitchell (founded 1911 in New York). It came together in its current form through a 1987 transatlantic mega-merger.
EY — Predecessor firms include Arthur Young & Co. (1894) and Ernst & Whinney, which itself traces back to an 1849 London firm called Harding and Pullein. EY as we know it formed in 1989.
PwC — Price Waterhouse was founded in London in 1849 by Samuel Lowell Price. Coopers & Lybrand also traces to 1854. The two merged in 1998 to form PricewaterhouseCoopers.
Scotland deserves credit here: in 1854, the Institute of Accountants in Glasgow received a Royal Charter from Queen Victoria, establishing the world's first formal accounting body. The "Chartered Accountant" designation was officially born.
From Big 8 to Big 5: The Merger Era
By the 1960s, eight firms had separated themselves from the rest of the market, auditing roughly 80% of all SEC-listed companies in the US. These were the Big 8: Arthur Andersen, Arthur Young, Coopers & Lybrand, Deloitte Haskins & Sells, Ernst & Whinney, Peat Marwick Mitchell, Price Waterhouse, and Touche Ross.
Then came a decade of consolidation. Between 1987 and 1998, four mergers compressed the landscape:
1987: Peat Marwick Mitchell merged with Europe's Klynveld Main Goerdeler to form KPMG
1989: Ernst & Whinney merged with Arthur Young to form Ernst & Young (EY)
1989: Deloitte Haskins & Sells merged with Touche Ross to form Deloitte & Touche
1998: Price Waterhouse merged with Coopers & Lybrand to form PricewaterhouseCoopers (PwC)
Eight firms became five. The industry still had Arthur Andersen — one of the biggest, most respected names in global professional services.
The Scandal That Created the Big 4
In 2001, energy giant Enron collapsed in what was, at the time, the largest corporate bankruptcy in US history. Investigators quickly turned their attention to Arthur Andersen — Enron's long-time auditor — and found that employees had shredded documents related to the audit.
Andersen was indicted for obstruction of justice. The conviction was later overturned by the Supreme Court — but by then it didn't matter. Clients fled, new engagements were blocked, and the firm filed for bankruptcy in late 2002. One of the most powerful names in professional services was gone in under a year.
The remnants were absorbed by the remaining firms: EY took the bulk of Andersen's global practice, Deloitte absorbed teams in the UK, Canada, Spain, and Brazil, and PwC took China and Hong Kong. Five became four — and has stayed that way ever since.
What This History Means for Your Career
The Big 4's dominance isn't accidental — it's structural. Understanding that structure gives you a sharper read on how each firm thinks and where the real opportunities are.
Know each firm's DNA: Culture and focus areas reflect merger history. Deloitte's consulting roots run deep. KPMG has strong European ties. EY absorbed significant Andersen talent. PwC's audit practice is among the most technically rigorous in the world.
Recognise the oligopoly: The Big 4 now audit 97–98% of FTSE 350 and S&P 500 companies, generating a combined $220 billion in revenue in 2025. That concentration means internal mobility and lateral moves between firms are both common and strategically valuable.
Track industry shifts: The Andersen collapse happened fast — within 12 months of the Enron story breaking. AI disruption, audit reform, and regulatory pressure are today's inflection points. Candidates who see them coming have an edge.
Use events to build early relationships: The Big 4 built their networks over 180 years. Find upcoming Big 4 events across all four firms in one place and get in the room while your peers are still reading about it.
Types of Big 4 Events Worth Attending
Each of the Big 4 runs regular events giving candidates direct access to partners, graduates, and hiring teams. Here's what to look for:
Insight days and firm tours — Get behind the scenes across each firm's main practice areas
Virtual open evenings — Low barrier to entry, high access to firm-specific careers content
Women in business events — All four firms run targeted programs with structured networking built in
Technology and AI showcases — Increasingly prominent across Deloitte, KPMG, EY, and PwC as AI reshapes their service lines
Graduate recruitment talks — On-campus and hybrid sessions aimed directly at final-year students
Your Next Move
The Big 4's rise from Victorian-era audit practices to a $220 billion global oligopoly wasn't accidental — it was built on mergers, timing, and the collapse of whoever stood in the way. Deloitte is the oldest. PwC runs some of the most technically demanding audits. EY absorbed Andersen's talent. KPMG has deep European roots. None of this is trivia — it shapes culture, hiring, and career paths within each firm.
The firms that dominate today adapted at every major inflection point. The same playbook applies to candidates navigating these organisations right now.
The candidates who understand where the Big 4 came from are better positioned to understand where they're going — and how to get in.
Start tracking the firms that will shape your career. Find upcoming Big 4 events — networking sessions, insight days, and graduate recruitment talks — all in one place.
