The BIG 4 or "Big Four" is a nickname used to refer to the four largest accounting firms in the US. They are:
Deloitte,
Ernst & Young (EY),
PricewaterhouseCoopers (PwC) and
Klynveld Peat Marwick Goerdeler (KPMG).
In addition to audit services, the big four offer tax, strategic and management consulting, valuation, market research, insurance and legal consulting services.
They recently started offering digital transformation consulting to meet the needs of the digital age. They are a leading source of tax law interpretation and experts in changing accounting and auditing standards.
With industry consolidation that began in 1989, what was once the Big Eight has now become the Big Four. The eight, in alphabetical order, were Arthur Andersen, Arthur Young, Coopers & Lybrand, Deloitte Haskin & Sells, Ernst & Whinney, Peat Marwick Mitchell, Price Waterhouse and Touche Ross - all US or UK entities.
Arthur Young combined with Ernst & Whinney and Deloitte Haskin & Sells merged with Touche Ross to reduce the number of groups to six. Price Waterhouse and Coopers & Lybrand then merged their practices to make five. After the collapse of Arthur Andersen, due to proven responsibility in the Enron scandal, the five of them became today's four.
These firms perform most of the audit work for some of the largest public companies in the world. In fact, the vast majority of Fortune 500 companies have their financial statements audited by one of the Big Four. Their clients include powerhouses such as Berkshire Hathaway, Ford Motor Co., Apple, Exxon Mobil and Amazon. According to a 2018 CFA Institute report, 30% of the S&P 500 was audited by PwC, 31% by EY, 20% by Deloitte and 19% by KPMG.
As of December 2020, the Big Four employ nearly one million people in total worldwide, or an average of 250,000 employees per company. According to their published reports, Deloitte reported the highest global revenue at $47.2 billion, followed by PwC at $43 billion, Ernst & Young at $37.2 billion and KPMG at $29.8 billion.
With a 360-degree view of companies and industries, the Big Four are the authority on the business. They have extensive recruitment and training programs for new graduates and sought-after gateways for tax and consulting professionals in and from many industry sectors.