套息交易拆倉一問。

In 套息交易, the most important thing is to borrow a low-yield currency then buy the high yield currency. Therefore, many investors will borrow JPY ( 日元) as JPY overnight interest rate stayed at 0.5% only, but for HKD (港幣), the overnight call rate stayed around 3.8%, hence HKD is not ideal to do carry trade. The investors will use the borrowed JPY to buy high yield currencies such as Australian dollar (6.75%) and New Zealand dollar (8.25%).
You might discover that investors will need to convert the borrowed JPY to buy AUD or NZD. There invloves a cost (exchange rate), say, 100 JPY for 1 AUD. If the exchange rate does not move, they will gain interest of (6.75%-0.5%) i.e. 6.25% per year. However, if the exchange rate drop to 90 JPY for 1AUD, investors will suffer a 10% loss on exchange which the interest gain (6.25%) can not compensate exchange loss (10%).