Why Not a Global Currency?

It appears likely that the number of currencies in the world, having proliferated along with the number of countries over the past 50 years, will decline sharply over the next two decades. The question I plan to pose here is: where, from an economic point of view, should we aim for this process to stop? Should there be a single world currency, as Richard Cooper (1984) boldly envisioned? Should there remain multiple major currencies but with a much stricter arrangement among them for stabilizing exchange rates, as say Ronald McKinnon (1984) or John Williamson (1993) recommended? Building on Maurice Obstfeld and Rogoff (2000b, d), I will argue here that the status quo arrangement among the dollar, yen, and euro (which I take to be benign neglect) is not far from optimal, not only for now but well into the new century. And it would remain a good system even if political obstacles to achieving greater monetary policy coordination (or even a common world currency) could be overcome. Again, this is not a paper on, say, the pros and cons of dollarization for small and medium-sized economies, but rather on arrangements among the core currencies. Any blueprint for the future core of the world currency system involves some crystal-ball gazing. But at the same time, recent research in international macroeconomics offers several important insights that can help inform the discussion.