Yet physical indicators (such as electricity consumption) and the results of income comparisons based on purchasing-power parity (PPP) suggest that the GDP picture may not be entirely misleading.

Once an economy reaches an income per person of about $15,000 (measured at purchasing-power parity), economic growth ceases to add to happiness, he says.

At purchasing power parity, China's real income per head was barely above a fifth of US levels in 2010.