Xi Jinping, likely to be China's next president, visits President Obama in the White House this week. This visit ensures that the ongoing currency war between the United States and China will be on the list of things that Obama and Xi discuss along with the looming war with Iran, the North Korean succession, and other geopolitical issues. Currency wars arise when a country steals growth from trading partners by cheapening its currency to promote exports. The new currency war began in 2010 when President Obama declared in his State of the Union address that it was the policy of...