As we discussed yesterday, if a nation's central bank lowers its interest rates, the usual expectation is that it will weaken its currency. Part of the reason why: it will set up a carry trade, in which profiteers will borrow money at its low rates, then exchange that currency for another currency, that issued by a higher-interest rate country, so these profiteers (I use the term without animus -- it simply means "those seeking a profit") can lend out for a higher rate than the one at which they are borrowing, pocketing the difference. This activity, given supply/demand principles predictably weakens the currency the profiteers are leaving and strengthens that into which they're moving. This brings us back to the mystery with which we began. Australia and New Zealand have both recently lowered interest rates. In each case, though, that has corresponded to a strengthening of the currency. Back in late May, you would have needed 1.39 Aussie dollars to buy a US do...