Opec’s core GCC countries peg their currencies to the US dollar, an anchor that has served them well given that it is the currency in which their key export is denominated. But as the third anniversary of the late 2014 collapse in oil prices approaches, debate is becoming more lively as to whether their currency pegs to the dollar still make sense. While opinion is divided, the consensus is that they will remain in place for now.    

The debate over whether the GCC...