The Chinese Renminbi (CNY) is a pegged currency and does not freely trade in the open market. Without going into too much fundamentals, the Chinese have kept the value of their currency artificially low. Due to pressures from some of its trading partners, like the U.S., they have slowly brought the value of their currency up which is why you see the steady decline of USD/CNY.
The interest rate in China is 7.47% and 3% in the U.S., so going short USD/CNY should give you positive 4.47% carry. But, brokers can basically set the interest rates they pay their clients, and I don't know the specific reason why, but my guess is they skew interest rates to protect themselves and their profit.
Imagine if a broker paid on real interest rates on USD/CNY, and all of their clients shorted huge...on 50 times leverage???? 200 times leverage?? With that kind of leverage, that would make the steady revaluation of CNY the trade of the century and brokers would get killed paying the interest on the carry.
Again, this is just my guess but the point is most brokers debit/credit what they want on carry and if carry is an important part of your strategy, you should definitely check out broker carry rates before you sign up with them.
I hope this helps
