Imagine all the investors and traders around the world moving their money to New Zealand to grab the 8.25 percent interest rate. The purchasing power of this global group is amazing: perhaps hundreds of billions of dollars worth of investment capital spread across all the currencies of the world. However, they cannot place their dollars, pounds, yen, francs, euros or such into the Bank of New Zealand. They can only deposit New Zealand dollars into their accounts.
Before investors from all around the globe place their money into the Bank of New Zealand, they must exchange their local currency for New Zealand dollars. This means they must to buy New Zealand dollars.