The "crisis of credibility" largely arose from the number of companies that restated their previously issued financial statements as a result of accounting irregularities and fraud. Especially responsible were the very visible Enron and WorldCom fraud cases. Both companies filed for bankruptcy and constituted the largest companies in American history to do so. The extent of the accounting irregularities and fraud being investigated and disclosed brought into question the effectiveness of financial statement audits. In addition, the criminal conviction of Arthur Andersen, LLP, one of the then Big 5 accounting firms, on charges of destroying documents related to the Enron case brought into question the ethical standards of the profession