Demography Won't Slow Down China Anytime Soon
First of all, I'm not sure whether The Economist has the fertility rates right. I can't find any official numbers from China, but in the United States it is more like 1.93 (in the link it is stated as 64.4 per 1000 woman in ages 15 to 44, so to get 1.93 you multiply 64.4 by 30 and then divide it by 1000) children per woman in reproductive age according to the latest official statistics, than the 2.08 The Economist claims it is
More importantly, the absolute number of births was still 16.04 million in China, slightly more than four times the 3.98 million in the United States. This means that the number of native born 25-year olds in China will be slightly more than 4 times more compared to the United States in 2036. The difference in the total number of 20-year olds in 2031will probably be somewhat smaller because the U.S. is likely to have some net immigration while China probably won't , but China will still have a nearly 4 times bigger working age population as late as 2036.