Pity the inter-bank currency brokers that deal for the world's biggest central banks.

Instead of the regular orders earlier this decade, the phones are now quiet. The Bank of Japan has not intervened in the foreign exchange market since 2004. It has been even longer for the US Treasury and the European Central Bank, with neither dipping a toe in since 2000. The hoo-ha over the Reserve Bank of New Zealand's attempts last week to stem the NZ dollar's rise highlights how rare interventions now are in the developed world.