We are talking about the numerical proportion and its impact. Yes, China is a large economy. I am just saying that 20% of Chinese economy, the export sector, is more crucial than the number 20% suggests. It is where most of net hard currecy comes out. The domestic sector may be big in numbers but they may not have robust foundations. As you may know, the pace of development in economy is not uniform along all sectors. Export sector is usually most competitive, and other sectors are slowly catching up, such as finance. It is natural in an economy like Chinese. You cannot change everything overnight at the same speed across the board. Especially, if Chinese financial sector is weak, external financial shock can inflict serious damage in Chinese economy, or any other economy in East Asia.
Slavery gives a nation obvious advantages.