I have posted some version of this explanation of credit default swaps in several threads, but it seems that it might be useful to DUers overall to understand what these things are and how they helped bring down AIG and Lehman.
Here is a explanation combined from several posts. Sorry for the cut and paste job:
Credit default swaps (cds) are a casualty not a cause of the mortgage backed security market collapse.
But they are a big, big problem, especially for AIG and Lehman, and did play a big part in driving them to bankruptcy.
A credit default swap is an insurance policy that a bondholder buys. Borrowing the colorful names used in the Wiki article on cds, let's say that Penion Fund wants to buy bonds from Risky Corp. It buys $10 million in Risky Corp's bonds which are 7% bonds for 5 years.
Risky Corp pays 7% interest or $700,000 each year. If Pension Fund gets scared that Risky Corp will default, Pension Fund can go to AIG and ask to buy a credit default swap.
Let's say the credit default swap costs 300 basis points (that's a fancy way of saying 3%). So Pension Fund pays AID $300,000 per year out of the $700,000 per year it gets from Risky Corp.
That may sound like a lot but it means (or was supposed to mean) that there was no chance that Penion Fund could lose money. If Risky Corp sends out a letter saying, we've run out of money we're not paying interest and may not be able to pay you your $10 million in year five, under the credit default swap, Pension Fund can go to AIG and say, here's Risky Corp's bond, we want our $10 million back and AIG has to give it to them -- even if Risky Corp's bonds are now selling for $2 million on the open market because of the default.
The worst thing about credit default swaps is that the repugs put a clause in the bankruptcy code that says that credit default swaps are basically exempt from waiting in line during bankruptcy if the issuer (AIG) of the credit default swap goes into bankruptcy.
That means that while AIG's bondholders, suppliers, employees, contractors -- everyone who was owed money -- would have had to wait in line if AIG had been allowed to go bankrupt, while the bankruptcy court tried to figure out how to pay off AIG's debts, holders of credit default swaps, like Pension Fund could just go and demand payment and get it.
Credit default swaps were purchased on trillions of dollars worth of mortgage backed securities, which means that the default of mbs means that certain issuers, like Lehman, are on the lines for billions and billions -- supposedly to be paid before bankruptcy even starts.
So, yes, effectively, holders of credit default swaps can force an insurance company into bankruptcy by "jumping the line" that the bankruptcy code was supposed to create. Corporate, banking and bankruptcy law create an elaborate system of who gets what first in the case of a bankruptcy. The repugs (Gramm?) inexplicably screwed up the entire elaborate hundred year old system by putting cds first and outside of bankruptcy.
The repugs also managed to get credit default swaps exempt from regulation as insurance policies. In my example, the insurance company was paid $300,000 per year to insure Risky Corp's bond. If this had been properly regulated like other insurance policies, AIG would have been required to put that $300,000 per year (and all the other money it collected in cds fees) in other super duper safe investments, in order to save up in case they had to pay off on the policy.
Again the repugs exempted cds from insurance regulations and made sure cds were treated as a derivative commodities (go figure, I'm as puzzled as you are on that one) rather than treated as an insurance policies.
So they didn't necessarily save up the premiums. Now that institutional investors are presenting failed bonds for payment of the insurance policies, the insurance companies -- and like Lehman companies playing at being insurance companies -- don't have the cash. Hence we have bankruptcy -- but worse, because the "line" has been screwed up.