As a socialist country, China will always be able to find work for the unemployed with so many mega-projects crying out to be done.
The low unemployment figure in the U.S. is largely due to the post-WWII Age Wave of baby boomers (those born between 1946-64) reaching retirement age. Since their numbers are huge, the fact that they aren't looking for jobs means they aren't counted in the lists. That's why the U.S. unemployment figures are lower than they had been in the past. In fact, this trend had already started in the Obama years.
Absorbing 20 million people is not that difficult for a country like China.