China's National Bureau of Statistics (NBS) has published the methodology it used to calculate the Gini coefficient reflecting the social wealth gap.

A new survey system was set up at the end of 2012 to unify the income index for 400,000 households in both urban and rural areas. Historical income data have been adjusted and recalculated, according to an article posted on the NBS website on February 1.

The reformed system has been drafted referring to international norms, wrote Wang Pingping, NBS Resident Survey Office chief.

Internationally comparable, China's recently released Gini coefficient reflects the income trend during the past decade, Wang said.

The 2003-12 Gini coefficients, ranging between 0.491 and 0.473, were released by the NBS on January 18. All the annual figures were much higher than the warning level set by the United Nations.