What a difference three decades can make. In 1980, China feared an explosion of people it could not feed, so it took drastic steps to limit births with its controversial “one child” policy.

Now, as the mainland starts its once-a-decade census, demographers say the world’s most populous nation has too few people in some areas and a critical shortage of workers and wives, which could threaten economic growth and social stability.

Whether because of the one child policy, or in spite of it, China’s birth rate has fallen sharply, and increasing numbers of families say they do not want more than one child. Shanghai, which demographers say has the lowest birth rate in the world, has launched repeated efforts to encourage procreation – but to no avail. According to one recent survey in the Oriental Post newspaper only 18.5 per cent of Shanghainese want more than one child.