China alone has more than 20% of the world’s population and India a further 17%. Together they will soon account for more than 40% of the worlds population. By contrast, at no time did the combined total of Japan and Koreas’ populations exceed 4% of the global total. China and India are also becoming increasingly integrated into the global economy, which means that the consequences of their growth are rapidly transmitted to other countries.
In other words, these economies are of such size that their growth, decline, trade, environmental and other impacts necessarily have a large impact on the rest of the world.
This is unlike the case of Korea, for example, which could grow rapidly for a very long period without by itself disrupting the global economy.