We refer to the dollar as a “reserve currency” when referring to its use by other countries when settling their international trade accounts. For example, if Canada buys goods from China, China may prefer to be paid in US dollars rather than Canadian dollars. The US dollar is the more “marketable” money internationally, meaning that most countries will accept it in payment, so China can use its dollars to buy goods from other countries, not solely the US. Such might not be the case with the Canadian dollar, and China would have to hold its Canadian dollars until it found something to buy from Canada. Multiply this scenario by all the countries of the world who print their own money and one can see that without a currency accepted widely in the world, international trade would slow down and become more expensive. In some ways, its effect would be similar to that of erecting trade barriers, such as the infamous Smoot-Hawley Tariff of 1930 that contributed to the Great Depression.

There are many who draw a link between the collapse of international trade and war. The great French economist Frédéric Bastiat said that “when goods do not cross borders, soldiers will.” No nation can achieve a decent standard of living with a completely autarkic economy, meaning completely self-sufficient in all things. If it cannot trade for the goods that it needs, it feels forced to invade its neighbors to steal them. Thus, a near-universally-accepted currency can be as vital to world peace as it is to world prosperity....