If you are lost in the sea of political mumbo jumbo about what has caused the financial crisis, this Vanity Fair article does really great job of laying the numbers bare.
The number is the first paragraph identifies that the world economic output was $48.6 trillion whilst the market capitalisation of the world's stock markets was $50.6 trillion and the total value of domestic and internals bonds was $67.9 trillion. These numbers are staggeringly large and impossible to fully comprehend (at least for a small mind/bank account like my own).
The article is long but extraordinarily useful for explaining how we got here and most importantly for putting it all in historical context. Take the time to read it.