China’s hidden household income totaled CNY6.2 trillion in 2011 – accounting for 12% of the country’s GDP – underlining the widespread impression corruption represents a “serious challenge” to society, according to a study by the National Economic Research Institute in Beijing. Most of this undeclared personal or household income comes from undocumented sources and is held by a few individuals, the study says. The analysis is based on a survey of more than 5,300 households in 18 provinces and 66 cities. The study results estimated the 2012 per capita income of the richest 10% of the urban population at CNY188,000 – 3.2 times more than the official figure. The urban rich make almost 21 times more than the poorest members of society. Official figures placed the gap at 8.6 times. “Corruption’s impact on society is expanding, posing a serious challenge to society,” the report said. Hidden income, also known as ‘grey income’, includes earnings ranging from utterly illegal activities such as bribes and off-book transactions, to gifts by parents to teachers. The study concludes the urban population had a Gini index of 0.5 in 2011, a higher figure than that released by the official National Bureau of Statistics (NBS) in January. The study cited loose monetary policy, exacerbated by lax regulations, as the cause of the swelling volume of hidden income. It pointed to the mismanagement of public funds, a lack of procedures regulating the economy, uneven income distribution triggered by monopoly holdings, government-determined monopolies in public administration, a lack of effective oversight of public power, and corruption in the public service sector. The first investigation into the subject in 2007 found a 55 times difference in income between China’s poorest and wealthiest groups in 2005, significantly greater than the official figure of 21 times, the South China Morning Post reports.