W hen Matt King, an analyst at Citi, started covering credit derivatives a few years ago, his clients tended to be investors with a specialist interest in the credit world.

This month, however, he is witnessing a striking change: many requests he receives about areas such as the oddly-named iTraxx index - a specialised European derivatives basket that can be traded as a contract - now come from across the markets spectrum. Traders in the yen-dollar market, for example, are now so hungry for information on iTraxx that they have asked Mr King for direct data feeds.