Like the gold standard of a century ago, the euro has promoted free trade and investment across borders. The 12-year-old unified currency also shares the gold standard's greatest flaw: the lack of an escape hatch. If a country runs chronic deficits, it can't regain competitiveness through the market's depreciation of its currency. Under the gold standard, exchange rates were fixed, which is to say the escape hatch of depreciation was locked. Under the euro, exchange rates no longer even exist. The escape hatch has been locked, welded shut, and sat on by the leaders of the Continent's most powerful economies.