As Stephen Roach, chief economist at Morgan Stan-ley, moved around the debates on the world economy in Davos last week, he admitted that some of the discussions were distinctly bland. With the world economy growing steadily, de-bates about big economic themes lacked real drama.

However, in one area there was a raging debate: the role that the fast-growing derivatives sector may, or may not, be playing in distorting the cost of credit.