Their titles vary and they come from around the nation, but there is one thing the 10 corrupt officials reported by whistle-blowers in the past two months have in common: each owned more than a dozen properties. From local police heads to bank executives, officials who own an unusually large number of properties - in an extreme case, one is suspected of having 192 - have been reported to authorities in the wake of the new leadership's call for citizens to help in the fight against corruption. Property, although relatively illiquid, is a favoured investment on the mainland because of the record high returns that it has delivered and the opportunity it provides to launder ill-gotten gains, economists say. "Property has always represented wealth, especially so after China's housing reforms in 1982, which sent property prices soaring," said Professor Hu Xingdou, a political analyst at the Beijing Institute of Technology. Under the reforms, property became merchandise for individuals to buy instead of housing assigned by an employer. Prices have been buoyant over the past decade as the rich and powerful snapped up investments and ordinary people scraped savings together to buy a place to live in. In major cities like Beijing, Shanghai and Guangzhou, prices have risen by more than tenfold over the past decade. In Beijing, luxury housing cost as much as 300,000 yuan (HK$373,000) per square metre in 2011 before regulators pegged back prices to avoid social unrest. Urban residents' annual disposable income was 21,810 yuan per capita that year. "In big cities there are plenty of rich people and corrupt officials, so someone owning 10 or 20 properties is hardly noticeable," Hu said. "Property is a bribe less traceable than straight cash, which leaves clues in bank accounts." Property is a bribe less traceable than straight cash, which leaves clues in bank accounts Faking a hukou , or proof of residency, could easily make the real owner of properties less visible. Zhai Zhenfeng , a former director of the housing administration bureau in Zhengzhou in the central province of Henan , and three family members all had two hukou and between them owned 31 properties, it was revealed in December. Reflecting robust demand for fake hukou , there was a thriving business in a county in Jilin , with a grass-roots police station charging 30,000 to 50,000 yuan for an extra hukou , according to Xinhua. Yuan Gangming , a researcher at the Chinese Academy of Social Sciences and Tsinghua University, said housing has the characteristic of being valuable but not high-profile. "More importantly, you cannot easily tell whether money used to buy property is clean or not, so it could facilitate laundering of illegal gains," he said. The transfer of ill-gotten gains into property has been rampant on the mainland in recent years because the government condones it, Yuan added. "The central government has been relying heavily on the real estate sector to drive economic growth, and thus it tolerates the plundering of wealth by the powerful," he said. No official data exists for the number of vacant properties, which would be an indicator of the severity of the situation. There is also no nationwide tax on property ownership and no estate duty on inheritance. These factors make property ownership low risk and low cost. Since November, a large amount of luxury housing has been dumped on to the market by sellers including government officials and senior managers of state-owned enterprises, spooked by the latest round of corruption busting, a source told The Economic Observer . Some 714 officials fled overseas between September 30 and October 7 last year, according to the Beijing newspaper.