gu

The most natural is "China has a fifth of the world's population" or "The Chinese are a fifth of the world's population." "Chinese" is wrong. "The Chinese" is correct. (p.152 - unit 7C - English Grammar in Use 4th ed. by Murphy (Cambridge). A PDF is probably available on the internet.) "count for" is incorrect. "account for" is correct. New Oxford American Dictionary count for • (count for) be worth (a specified amount): he has no power base and his views count for little. account for 2 supply or make up (a specified amount or proportion): social security accounts for about a third of total public spending.