The National Bureau of Statistics (NBS) publicized its methods for compiling the Gini coefficient over the weekend and admitted that it is hard to get access to some types of household income, following queries about the accuracy of its data by some academic institutions and media reports last month.
By December last year, the NBS had collected samples of 140,000 urban and rural households from 31 provinces, autonomous regions and municipalities involving 896 counties and 476 cities and towns, according to an article published Friday by Wang Pingping, director of the households' investigation office under the bureau.
To improve the accuracy of the Gini coefficient, which measures income inequality, the NBS set up a new sample system and began to collect samples from 400,000 households starting from December 1, 2012, the article said.
The specific calculation formula, sample collection procedures and measures were also laid out in the article.
"The calculation formula is okay, but some important details of the original figures for the calculation have still not been disclosed," Gan Li, the director of the Survey and Research Center for China Household Finance under the Chengdu-based Southwestern University of Finance and Economics, told the Global Times Sunday.
"The bureau needs to disclose the percentage of interviewees who declined to receive the NBS' investigations during the sample collection procedure," Gan said. Gan's institute produced its own Gini coefficient in 2010 with a reading of 0.61.
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