The value of the most collectible Chinese postage stamps is up 46% pa since March 2009, according to new figures, with China's increasingly wealthy inhabitants thought to be behind the surge.
The China 100 Stamp Index tracks the auction performance of 100 stamp sets from the Qing Dynasty (ended 1911) to late 20th century specimens.
Starting with a figure of 100 in March 2009, the index stood at 238 in February 2012.
"During the Cultural Revolution, Chinese people were too poor to buy stamps," Ricky Tam Siu-hing, one of the founders of the company behind the index, told Hong Kong's The Standard newspaper.
"Now as they are wealthier, many would like to collect them."
He added that the index has outperformed more traditional investments such as the stock market and property during the same time frame.
The index includes stamps such as the Red Revenue Large $1, Mei Lang Fang souvenir sheet, as well as the much in-demand Chinese monkey stamps, produced in 1980 to celebrate the year's Golden Monkey zodiac sign.
The world record for a sheet of Chinese monkey stamps has been broken four times in the past two years.
A sheet of the stamps sold for HK$1.49m ($192,000) at a Hong Kong auction in September 2011, marking a 186% increase in price since January 2010.
A recent report by the Hurun Research Institute states that one in 1,400 Chinese citizens is now a millionaire, while figures from the Boston Consulting Group indicate there were 670,000 Chinese millionaires in 2009, up from 190,000 in 2004.