Big 4

The Big 4 refers to the world's largest audit firms. In order, these are:

• PricewaterhouseCoopers
• Deloitte
• KPMG
• Ernst & Young

A list of accountancy firms and auditors can be found here.

The Big 4 was once the Big 6 until 1998. A merger of Coopers & Lybrand and Price Waterhouse to form PricewaterhouseCoopers reduced this number to 5. Following the collapse of Arthur Anderson in 2002 due to the Enron scandal, the number of large auditors was reduced to just four. In a shrewd business move, Deloitte re-employed 50% of Anderson's staff and embodied them into their firm, absorbing their clients along the way, in what was to be known as the Anderson transaction.

A detailed history of the world's largest auditors can be here.