Some fairly simple math indicates that it wouldn't take much to wipe out the capital of the banks and hedge funds. And this simple math helps explain why the popular delusion that 'liquidity' = 'capital' is so dangerous. That mental equation works just as easily to create the illusion of prosperity as it does to eliminate the capital that is supposed to stand as bulwark against bad lending decisions.

That's because investment banks and hedge funds combined have borrowed $10.9 trillion on a sushi-thin slice of equity of $340 billion. Newsweek reports that on average, the ratio of borrowed money to underlying capital for investment banks and hedge funds is about 32-1. It reports that in 2006, investment banks had an estimated $280 billion in capital. At 32-1, the investment banks are borrowing $8.96 trillion. Meanwhile, hedge funds manage $1.9 trillion worth of assets – which would represent $60 billion in equity and $1.94 trillion worth of debt.

What would it take to gobble up that little piece of sushi? Well, collateralized debt obligations (CDO) represented a $6.1 trillion market. I say 'were' because I am guessing that this figure refers to the value of the CDOs when they were issued. And CDOs seem to be worth some amount below that now. I have seen estimates that they are worth 20 cents to 40 cents on the dollar of their original value.

But if investment banks and hedge funds had used all their money to buy these CDOs, then it would take a mere 6% decline in their value to wipe out that $340 billion in capital. Obviously investment banks and hedge funds have invested in other things besides CDOs. But when you borrow $32 for every dollar in capital, there's not much room for error.

Peter Cohan is President of Peter S. Cohan & Associates. He also teaches management at Babson College and edits The Cohan Letter.