While Central Committee meetings do not usually serve as forums for substantive debate, they have sometimes 'fine-tuned' the policies agreed upon at the Politburo level. But the Central Committee does not, by convention, overturn policies decided at higher levels. The Central Committee is larger and has a somewhat more diverse ideological spectrum than the Politburo. Since its plenary sessions is a rare event that concentrates almost all of China's top leaders in one location, it could also be seen as a convenient venue for informal deal-making.