Countries that only use a foreign currency

US dollar: Ecuador, East Timor, El Salvador, Marshall Islands, Micronesia, Palau, Turks andCaicos, British Virgin Islands, Zimbabwe.

The US dollar is the most widely used currency in the world, with many countries employing it asan accepted alternative to their own currency. But some have simply adopted the currency as theirown, notes and all, in what is known as "dollarization." They don't have control over thecurrency-only the Federal Reserve in Washington sets monetary policy. Both Ecuador and El Salvadoradopted the US dollar in 2000, following the creation of free-trade blocs like NAFTA and the EU andthe debut of the euro, making even the notion of a "single currency for the hemisphere moreplausible and attractive."

Countries in a currency union

Euro: Austria, Belgium, Cyprus, Estonia, Finland, France, Germany, Greece, Ireland, Italy,Latvia, Luxembourg, Malta, the Netherlands, Portugal, Slovakia, Slovenia, and Spain.

Calls for monetary union in Europe date back to the 1920s, but things got serious when theEuropean Commission (of the European Economic Community, precursor to the European Union) beganlooking into ways to stabilize fluctuations between the their currencies in the late 1960s. In1989, the path to monetary union was set out in the Delors report. In 1992, the Maastricht Treatywas signed, which created the EU and set up the path to the launch of the euro in 1999. In 2002,euro notes and coins entered circulation.

There are extensive criteria to join the euro, but nothing in the EU treaties about leavingit-which was unfortunate, as many countries' finances came under severe strain in the aftermath ofthe 2008 financial crisis. (None more so than Greece, which at one pointed owed $250,000 for eachworking adult.) While the euro looked doomed for awhile, the problem was solved using one of thebest traditions of capitalism: throwing more debt at the problem. Greece was bailed out-twice-andthere was one bailout each for Portugal, Ireland, and Cyprus by the euro zone countries and theIMF. Spain's banks were bailed out, too, and a 500 billion-euro fund was set up to permanently actas a firewall to prevent this from happening again.

Alternatively...

Many places both officially and unofficially allow the trade of foreign currencies alongsidetheir own. Residents from Belize to North Korea can spend in US dollars, for example. Panama hashad the US dollar as legal tender since 1904, alongside the Panamanian balboa, and was viewed as aspecial case in Latin America because of the Panama Canal and its huge trade links with the world'srichest country. Others are usually based on relative economic might and regional proximities;Lesotho and Namibia also use South Africa's rand and small islands like Tuvalu and Nauru useAustralian dollars.

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Here are allthe countries that don't have a currency of their own(qz.com/260980/meet-the-countries-that-dont-use-their-own-currency/)