China’s Plunging Yuan Is a Bigger Deal Than Elon Musk and Twitter

While your attention probably was focused on that big takeover of a certain social-media site, the gyrations in the global currency markets arguably were even wilder and probably more important.

Asian currencies, notably China’s yuan and Japan’s yen, took their sharpest dives in years, while on the other side of the globe, the euro slid to a five-year low. To be sure, much of the drops reflects the strength of the greenback, resulting from the surge in U.S. bond yields this year. But there are other, particular aspects that...