The system collapsed after the imbalances between Europe and the United States became impossible to reconcile. Rapid growth is putting similar pressure on China, which has kept its currency, the yuan, pegged at a fixed rate to the dollar.

The growing imbalances, in both China and the United States, is one reason Mr. Rogoff is bracing for a jolt to the dollar and the American economy similar to the one that occurred in the early 1970's.

Then, as now, the United States was running large budget and trade deficits. Then, as now, the United States was bogged down in a war costing billions of dollars a year. And in 1974, a few months after the dollar plunged against the German mark and Japanese yen, oil prices soared.

"It's striking how many parallels there are between today and the early 1970's," Mr. Rogoff said. "The loss of the anchor of the dollar and fixed exchange rates contributed to the inflation we saw in the 70's. It was the worst period in growth we have had since World War II."