Joe Ucuzoglu, Janet Truncale, Bill Thomas, and Mohamed Kande — the leaders of the Big Four.EY/EY, Deloitte, PwC, and KPMG make up the world's largest accounting and consulting firms — known as the Big Four.The sector is tackling a slowdown in demand, new regulatory pressures, and the need to adapt to AI.These are the four leaders that have made it to the top of the firms.EY, Deloitte, PwC, and KPMG make up the world's largest accounting and consulting firms, known as the Big Four.They're billion-dollar companies with a collective 1.5 million staff and influence over hundreds of industries.In recent years, the Big Four have faced a series of challenges, including a post-pandemic downturn in demand, shifting regulatory requirements, and the need to adapt their skills and services for the emerging AI future.Two of the firms appointed new leaders in 2024.