Dark clouds of suspicion hover, ominous as a Beijing rainstorm, over the reliability of China's economic data. Everyone from confirmed China bears to panda-hugging investment-bank analysts wonders whether growth is lower than the official statistics suggest.

China Real Time has sent a sternly worded fax to Zhongnanhai demanding to know how fast China's economy is really growing. If no response is forthcoming, we are willing to take the next step of asking an intern to call the switchboard.

To fill the time while we wait for the Great Wall of Statistical Secrecy to crumble, we have constructed a data set on China's economy entirely from private and foreign sources, untainted by the suspicion of political interference. This is what it says.

Industry is the biggest chunk of China's economy, accounting for almost half of total output. The official data has industrial output growth chugging along at a respectable 9.5% year-on-year in June.

Independent surveys conducted by HSBC Markit and Market News International suggest the real situation might be worse. Flash readings on both the HSBC PMI (which is weighted toward small private firms) and the MNI survey (which has a bias toward big state owned enterprises), came in below 50 in July -- suggesting contraction in the manufacturing sector.

Sales of excavators, emblematic of the state of construction and machinery firms, also paint a bleak picture. Unit sales dropped 19% on-year in June according to numbers from China Construction Machinery Business Online.

A look at the operating income of firms in the industrial sector provides a slightly more optimistic read. Income for mainland listed manufacturing firms grew 8.7% on-year in the first quarter, compared to 28.3% in 2011, according to numbers from data provider CapitalVue.

Income for the construction, real estate and utilities sectors was more stable, with on-year growth comfortably in double digits in the first quarter. Most firms have not yet released earnings data for the second quarter.

Investment contributes the lion's share to China's demand. And within investment, the real estate sector does a lot of the work -- accounting directly for 12% of China's gross domestic product, according to the International Monetary Fund.

Two years of government-imposed property controls - an attempt to bring down sky-high house prices - have knocked housing demand down a notch. Numbers from private real estate agency Soufun suggest that sales are now creeping back up.

Sales in Beijing, Shanghai and other major cities have been on a rising trend since the beginning of the year. Du Jinsong, China property analyst at Credit Suisse, says construction could start to rebound in the second half.

A big chunk of China's investment is in infrastructure. Data from China State Construction Engineering Corporation -- a massive state-owned conglomerate that builds China's bridges, roads and other public works -- suggests building has slowed, but not ground to a halt. Revenue in the first half was up 15% on-year, down from 87% growth in the same period of 2011.