China's fertility rate has been below the level needed to sustain its population numbers since the early 1990s

Even before the 'one-child policy' was introduced in 1979, Chinese fertility rates were in decline. For the last three decades the average number of children born to women has been below two, meaning that population shrinkage is inevitable without immigration. 

Chart: The Conversation, CC-BY-ND Source: The World Bank Get the data