The Chinese yuan’s 6 percent decline over the past five months is hardly anyone’s idea of a crisis. On average it comes out to a drop of less than 0.04 percent a day. But behind the scenes, Chinese policy makers are unleashing a torrent of measures to stabilize the currency and prevent it from tumbling. Added up, these efforts rival some of the biggest currency defenses seen in emerging markets over the past two decades. Here’s a quick look at the central bank’s most aggressive steps. Hong Kong has become a key focal part for policy makers. Over the last two days, they bought enough yuan there to push overnight borrowing costs for the currency to a record 67 percent on Tuesday from just 4 percent at the end of last week. These rates, designed to discourage speculators, are even higher than those at the peak of Russia’s defense […]