They stopped the one child policy nine years ago; they had it in the first place because demographic projections had them severely overpopulated if they didn't.
During the period in which it was active, their GDP increased by a factor of about 62. Not percentage, multiple.
They reversed the policy too late. Their rapid growth was them seizing the low hanging fruit upgrading from a country of almost entirely peasants to slightly fewer peasants, all funded by Western greed. Those gains will never happen again.
During the period in which it was active, their GDP increased by a factor of about 62. Not percentage, multiple.