Argentinian President Mauricio Macri’s government has asked the International Monetary Fund for a loan that it hopes can stem a peso rout that has driven up interest rates, will slow the economy, and threatens the reform program. This reversal of fortune for the economy partly, though far from fully, reflects broader pressure created by the US dollar’s recent appreciation – a process that is set to accelerate, because both monetary-policy and growth differentials are now favoring the United States.