During the recent meltdown of the US subprime mortgage market, the ABX derivatives index became a popular barometer of negative market sentiment. More lately it has had to fight a growing irrelevance but, with buyers at last starting to emerge for distressed mortgage securities, a new opportunity for the ABX is presenting itself.

Banks on Wednesday began trading a newly constructed addition to the ABX. This tracks the performance of a portfolio of subprime mortgage bonds and has risen rapidly in investor consciousness as a favoured way to bet on the subprime collapse.