How much in, out

"Before doing the statistics work, I didn't understand what the CPI was. It seemed so far from my daily life," said Huang Bangzhi, 47, a rural bookkeeper for the bureau's urban and rural household survey office in Wanzhou district, Chongqing.

Huang was randomly selected for the job, and this is his second year recording his family's daily income and expenditures. According to the bureau, each rural bookkeeper needs to keep accounts for five consecutive years.

The statistical survey of daily income and expenditures is another basic component in setting the weights of different goods and services in the CPI basket as well as other indicators that can reflect the macroeconomic scenario.

Income data is the key reference to determine the minimum social security level, the income tax threshold and the nation's wage rates. The expenditure data is the basic source for analyzing people's consumption structure and customs - what they buy and how or how often.

Looking at Huang's account books, for January 2011 his family income was 3,880 yuan, including government subsidy and the revenue of his snack shop. On the expenditure pages, Huang wrote down payments for different products and services in terms of standard units. For example, on Jan 3, he bought 2 kilograms pork; cost 24 yuan.

"The most troublesome work is that I have to record each payment, even for one soap or one bottle of cola," Huang said.

In the first two months, Huang spent about two hours keeping these accounts every day. "At the beginning, I felt so impatient in this work and I always missed some expenditures. But after taking training from the Statistics Bureau, I can make clearer notes and it only takes me 10 minutes a day," he said.

"I am pleased to keep the accounts now because I know it is very important to know the country's true household consumption level. Now I pay close attention to the monthly CPI figures that I have contributed to."

For the five-year period that started this year, 140,000 families have been selected through a stratified random sampling method to keep the daily books. Of these, 74,000 are from rural areas in 896 counties, while the rest are urban families. It is one of the world's largest national statistical systems.

According to the China Statistics Law, keeping daily income and expenditure accounts is one of the residents' obligations. However, there are no coercive measures that force people to do the work. It is a part-time job for bookkeepers, and it pays 40 yuan ($6.30) a month.

Trustworthy?

In the first three quarters this year, per capita total income in urban areas was 17,886 yuan, an increase of 11.9 percent from a year earlier. Rural residents' cash income was 5,875 yuan, up 20.7 percent from a year earlier, according to the bureau. (For urban residents, income includes both cash and income from capital assets.)

Bureau spokesman Sheng Laiyun said at a news conference last month that many workers' wages could rise quickly because of increasing company profits and the 20 percent average growth in the nation's minimum wage threshold.

Tom Orlik, Beijing-based columnist for The Wall Street Journal, thinks that China's economic data can't be trusted for a couple of reasons.

Because of the sheer size and complexity of the world's second largest economy, statisticians can be defeated by many technical challenges, Orlik wrote in his book Understanding China's Economic Indicators. In addition, he said, some local governments may "decorate" the data they report to the central government to win political advantages.

However, Orlik noted that the bureau has conducted more surveys and scrutiny of the accuracy of data collected locally, and that more data is reported directly to bureau headquarters in Beijing, escaping the interference of local leaders.

"These checks and balances have freed the national-level data from the impact of local exaggeration," Orlik wrote.