The "Big 4" audit firms - PricewaterhouseCoopers, Ernst & Young, KPMG, and Deloitte - dominate the global financial audit market. While they audit most large multinational companies, concerns have been raised about risks to audit quality from a lack of competition. Some proposals to address this include mandatory audit firm rotation or increased regulatory oversight of the audit process. However, others argue this could increase costs for companies without necessarily improving quality. Overall, there is debate around how to strengthen independence and effectiveness within the concentrated global audit industry.