Privately held wealth on the Chinese mainland hit 80 trillion yuan ($13 trillion) in 2012, with more than 700,000 individuals now holding 10 million yuan or more in investable assets, more than double the number at the end of 2008, according to a new report.

But the annual growth rate of private wealth moderated between 2010 and 2012 to 14 percent, from 28 percent between 2008 and 2010, amid an economic slowdown.

The findings, from China Merchants Bank and US-based management consulting firm, Bain & Co, showed that the richest on the mainland are stepping up their investment in foreign assets as they try to preserve their fortunes in the face of uncertain economic prospects.