The Reserve Bank says its $100 billion bond-buying program has lowered long-term yields by 0.3 per cent and has helped keep a lid on the Australian dollar, despite currency and bond markets moving in defiance of the central bank.

In its first detailed assessment since the RBA kicked off its long-term bond-buying program in November, the central bank said the $5 billion a week of state and federal government purchase was having the desired effect.