The absence of authoritative figures on the nation's housing vacancy rate, reported as high as 50 percent in major cities by domestic media, has led some netizens to carry out a field investigation themselves.

Initiated by news portal Sina.com, a nationwide investigation was conducted on the housing market in more than 100 cities, with many netizens volunteering to collect firsthand information by counting the vacant rooms in commercial buildings.

"With help from our users, we have gathered information on more than 1,000 real estate projects across the nation so far," said Liao Lanxin, an editor in charge of the online survey from the Shanghai office of Sina.com.

"Counting black rooms at night is a direct way to find out whether an apartment is occupied or not," Liao said. Of the 100 Shanghai property projects the website researched, volunteers found that 51.23 percent of the flats were empty. The no-lighting rate in the Beijing properties polled is 65.6 percent. Hainan was the highest with more than 70 percent black, she added.

On Aug 4, China's National Bureau of Statistics (NBS) said that as of June 30, the unsold housing area across the nation totaled 191.82 million square meters, up 6.4 percent over a year earlier. However, NBS didn't release any data on the much-talked about housing vacancy rate, adding that accurate figures depend on the future population and housing census.

"There are no official and reliable figures to reflect the vacancy rate in the current housing market, but for those who care about the healthy operation of the market, we feel responsible to do the research," Liao said.

Using the most direct and grassroots methodology by counting the rooms with lights on, netizens get a look at the current housing market, she added.

Of more than 10,000 online users polled, 91.1 percent said the number of unoccupied properties is outrageously high in their cities. Some 88.8 percent polled said that property prices are directly pushed up by speculators who buy a number of houses and leave them vacant.

"Investors-owners leave their properties vacant just because they can relish the gains from the soaring housing prices even if they don't lease them out," said an employee named Ma Li, who works at a trading company in Shanghai.

"My landlord has four other apartments after leasing one of them to me, and he has made himself a multi-millionaire by buying houses with mortgage loans over the past decade," Ma said.

Lu Qilin, director of the Shanghai-based Uwin Real Estate Research Center, told China Daily that he understands why netizens want to know the truth about China's housing market after official bodies failed to offer such data. But Lu doubted the accuracy of counting lights to obtain the vacancy rate.

"Surely some of the high-end apartments are not used, but this methodology is arguable in terms of effectiveness," he said. According to him, all the apartments in Tomson Riviera, once known as "China's most expensive apartments", have their rooms' lights on at night, even if they are vacant, so the no-lights method is not reliable.

"On the other side, there must be housing owners who have good light-proof curtains and those who go on a business trip. All these should be factored in, or its accuracy is dubious," Lu added.

Chen Sheng, director of the China Index Academy in Shanghai, said the netizen activity shows the public, especially those who cannot afford the soaring housing prices, wants to bring the distorted housing situation to public light.

"Housing spending plays an increasingly greater role in Chinese consumers' life. As we know, more than 60 percent of a family's daily expenses goes to buying or leasing an apartment. In this case, social fairness and government subsidies for the poor is of great importance and urgency," said Chen.

To curb the housing prices from soaring higher, the central government imposed its harshest property policy in recent memory in April. But the housing market has only seen a shrinking trade volume, while the property price nationwide continued to rise over the past three months. Housing prices in China's 70 major cities rose 10.3 percent in July year-on-year, according to the latest figures released by NBS on Tuesday.