The air quality in Beijing and Shanghai is among the worst in the world. As much as 80% of Chinese cities do not meet the minimum standard. Although measures are being taken to improve the quality of the air by moving or closing down old factories, Beijing currently has five million cars, which is four million more than fifteen years ago. Many buildings are demolished and new ones are built in their place, which causes a lot of dust. But the biggest problem of all is the population, which has doubled in that period to 20 million.
What would that number have been in China without the one-child policy?