Renowned strategist Jeremy Grantham, founder of US asset manager GMO, estimates individuals in the US have suffered a $20 trillion loss of wealth in the past 15 months -- but their riches were mostly illusory in the first place.

This illusion was worth $50 trillion at the market's peak in 2007, according to Grantham. In his quarterly review he writes: "How could we kid ourselves that we were suddenly rich and didn't need to save for our pensions when were sitting in the very same buildings we bought in 1974? We have not lost wealth, but just the illusion of wealth."