This study divides the world into currency zones according to the co-movement of each currency with the key currencies. The dollar zone groups economies that produce well over half of global GDP. The euro zone now includes almost all of Europe and some commodity producers, but remains less than half the size of the dollar zone. The dollar zone share has shown striking stability despite big shifts across zones over time. These include the demise of the sterling zone and the expansion of the DM/euro from northwestern Europe to Europe and beyond.