Pegged to the U.S. dollar since 1983, the Hong Kong dollar is usually a dull currency. Except when it isn’t. While its trading band of HK$7.75 to HK$7.85 per U.S. dollar, set in 2005, has never been broken, it keeps getting tested. That forces the Hong Kong Monetary Authority, the de-facto central bank, to follow its mandate and intervene, raising questions about how long this can continue and the implications for Hong Kong’s wider economy.