BEIJING - China's National Bureau of Statistics (NBS) on Tuesday announced adjustments to the decade-old method it uses to measure the country's production and investment indicators, saying the changes would help improve the accuracy and timeliness of statistical data.

Beginning January this year, China had revised up the statistical threshold of "large-scale" industrial enterprises to measure only those with an annual business income above 20 million yuan ($3.04 million), from the previous 5 million yuan, when compiling industrial production data, the NBS said in a statement on its website.

For fixed-asset investment data, China will survey projects with total investments of more than 5 million yuan, up from the previous 500,000 yuan, while bringing projects in rural areas into the statistical count, NBS said.

Enterprises that are above the new statistical criteria will be surveyed one-by-one, while those under-criteria companies will be calculated by sample surveys, NBS added.

The previous monthly economic indicator of "urban fixed-asset investment" has been replaced by "fixed-asset investment (excluding rural household investment)" to include those investments in rural areas, according to NBS.

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"The revisions are important moves by the statistics departments to improve the accuracy and effectiveness of statistical data in accordance with the new changes in our country's economy," the statement said.

Further, the State Council, or China's Cabinet, has approved the revisions in statistical criteria, according to the statement.

NBS had used the current methods to measure China's key economic indicators since 1998 when the country's gross domestic product (GDP) was only 7.9748 trillion yuan, compared with 39.8 trillion yuan in 2010.

According to NBS data, the number of projects with fixed-asset investments of more than 500,000 yuan jumped to 661,000 in 2010 from 159,000 in 1997 when the previous statistical criteria was first applied.

Meanwhile, the number of large-scale enterprises with their annual business incomes above 5 million yuan more than tripled to 434,000 from 165,000 in 1998 when China began using the previous statistical method.

"Though the number of fixed-asset investment projects was down using the revised criteria, the impact on the total investment volume figure was limited," said an NBS spokesman.

Using the new 5 million-yuan criteria to calculate the fixed-asset investment indicator, the project number was down by 23.5 percent, though the total investments dipped only by less than 2 percent, said the spokesman.

For measurement of industrial production indicators, the 20 million-yuan new statistical criteria reduced the number of targeted enterprises by 40.6 percent in 2009, but the country's industrial value-added output growth data was down by only 2 percent, business income data down 3.4 percent, assets down 5.5 percent and profits down only 1.3 percent, according to NBS.

NBS is due to publish the two indicators and other key economic data, such as consumer price index, producer price index, retail sales figures and industrial value-added output growth for February on Friday.