One last thought: Although the Roach-Frankel duo went on to address currencies and exchange rates, the two never got to a basic risk factor in the current fragile period: What if the U.S. dollar, under the weight of private and public misallocation of resources, were to collapse?

FORBES: Deficits hinder investment? 'Ludicrous'

Rates and Currencies revenues also declined, as growth in Local Markets, which includes rates and foreign exchange trading primarily in emerging markets, was more than offset by lower G10 Rates trading revenues.

FORBES: Citi Shares Could Swirl Down The Drain As Fixed-Income Revenue Withers

Rates and currencies revenues also declined, as growth in local markets, which primarily includes rates and foreign exchange trading in emerging markets, was more than offset by lower G10 trading revenues.

FORBES: Citi Shares Could Swirl Down The Drain As Fixed-Income Revenue Withers

In order to maintain exports and to manage economic expectations, many nations (most notably China) have instituted fixed exchange rates between their own currencies and the U.S. dollar.

FORBES: Germany And China Have The Gold And Will Make The Rules

Tokyo has started a new carry trade, in which global investors borrow yen at ultra-low interest rates, exchange it into other currencies and invest for a higher return.

WSJ: Review & Outlook: Abenomics Hits the Neighbors

Households and companies have borrowed in hard currencies, believing that their exchange rates could only harden against the euro in advance of joining it.

ECONOMIST: Has the IMF changed? Or has the world?

The exchange rates between different currencies provided a mechanism for adjusting to shocks and economic events which affected different countries differently.

FORBES: Friedman and Roubini on the Euro Breakup