THIS afternoon, I listened to Axel Leijonhufvud give a very interesting (and scary) talk at the Graduate Institute in Geneva about the financial crisis. He spoke about many things, but his account of the "unexploded bomb" of credit default swaps disturbed me. Others have written on CDS, but until today I didn’t really get it. Here is how I make sense of it.

Fact one—there are several dozen trillion dollars of these things out there—an amount that makes Paulson’s $700 billion look like a rounding error.

Fact two—they are basically insurance policies on bond defaults that are written without regulation, so the usual insurance-industry practice of setting aside reserves does not apply. Oh, and while the premia enter as bank income the pay-out obligations are not on their balance sheets.

Fact three—the large banks think they are hedged since they have "insurance policies" on both sides of the default events. Hedged? In normal times, perhaps. But imagine if one big issuer of these insurance policies went broke at roughly the same time that one of the insured bonds went bad—say, for instance, Ford bonds and a major Wall Street bank headquartered in Europe.

The Ford bond default would trigger a call for a huge payout by many banks, but the disappearance of one of the major issuers would wipe out the hedge that many other banks thought they had. This would leave banks liable for a huge payout for which they would have no reserves. This could trigger a wave of failures that would be very hard to stop given the size of the market.

Here is an account on Eurointelligence (from February 2008) of where the CDS' "unexploded ordinance" problem stands. Satyajit Das writes:

The CDS market entails complex chains of risk. This is similar to the re-insurance chains that proved so problematic in the case of Lloyds. … Over the last year, securitisation and the CDO (collateralised debt obligation) market have become dysfunctional. As the credit crisis deepens, the risk of actual defaults becomes real. Analysts expect the level of defaults to increase. The CDS market is about to be tested. While there have been a few defaults, the market has not had to cope with a large number of defaults at the same time. CDS contracts may experience problems and may be found wanting.

I hope the geniuses in the American and European governments are working on a contingency plan for a meltdown in the CDS market. Given the size of this unexploded ordinance, let’s hope they are working on it together.