Was it just a mirage? The stronger, more synchronized growth in the world economy that powered markets in 2017 has faltered at the start of 2018. As that has become ever clearer in recent weeks, the U.S. dollar has rebounded suddenly and surprisingly. The uncomfortable reality is that economic, financial and monetary-policy cycles are in very different places around the world.
On the growth side, Wednesday’s first-quarter eurozone gross domestic product data confirmed a slowdown, with annualized expansion falling to 1.7% from...