Arthur Andersen went out of business after Enron and the big five became the big four. Maybe that was a good outcome in terms of accountability but there needs to be some effective process for promoting new members if we are going to keep culling this club.

Arthur Anderson if I’m recalling correctly didn’t go out of business so much as pushed out of business not fairly or completely legally by the feds.

They didn't go entirely out of business: their consulting arm is now known as Accenture.

The split happened prior to the Enron bankruptcy and was the result of a decade of litigation (Andersen consulting partners weren't happy with the profit-splitting with the audit partners).

One of the big 5 was banned from Uk government work for decades over the Delorean Scandal.