Credit protection sanity

I have made a bit of a sideline in highlighting some of the less helpful comments on the CDS market. It pains me to include a man I generally respect, Paul Krugman, in the list of people who have got the wrong end of the stick.

He first quotes marketwatch:

The spreads on credit-default swaps for U.S. government debt jumped to 97 basis points Tuesday, nearly seven times higher than a year ago and 60% higher than the end of last year, to a level roughly in line with those of France, according to data supplied by Markit.

Then he opines:

Has the risk of a US government default risen? Probably. Nonetheless, the people buying these contracts are crazy. A world in which the US government defaults would be a world in chaos; how likely is it that these contracts would be honored?

The answer is that it does not matter (much). Most CDS trading is about views on the spread, not views on default. People buy CDS on the US government because they think the spread will widen and they can close out at a profit, not because they think that default is likely. Therefore the CDS market often tells you rather little about default: what it tells you about is market participants expectations of spread movements. CDS spreads go out when there are more buyers of protection than sellers. That is the only reason spreads move. Any connection between CDS spread movements and expectations of default is a modeling assumption, and one that is particularly dubious at the moment.