When Lin Xu, an office worker, crams himself into a tight suffocating bus every morning, sometimes with his face pressed against a window, he can't see what could possibly be wrong with China's one-child policy.

The family-planning policy was introduced in the 1970s to encourage late marriages and late childbearing. It limited most urban couples to one child and most rural couples to two children. It is estimated that without the policy, the country's population would have ballooned by 400 million more than the current 1.3 billion, according to the National Population and Family Planning Commission.

But there is a price to pay. Recently, the aging workforce and its social problems have forced Shanghai into allowing eligible couples to have two children, a move that has triggered widespread speculation of a policy shift.