Between 150-250 million Chinese have moved within China sine 1978 which is the largest migration in history.
Net losers are China'scentral provinces whereas coastal areas to the east are major gainers.
Most migrants moved from rural provinces to urban areas on the coast.
1978: On the eve of economic reforms, 20% of China's population lived in cities.
By 2020: 60% of China's population lived in cities.
Relocation of millions of rural people gave many Chinese cities a 'site factor' certain to attract FDI: a large and cheap labour force.
The Chinese government's authorisation of free movement can be viewed with hindsight as a rational economic decision allowing China to benefit from globalisation.
The 'migrant miracle' that followed underpinned 30 years of rapid economic growth.