In 2017, the RBA cash rate was just 1.5 per cent. Today it is 4.6 per cent.
Look only at those numbers and monetary policy today appears vastly tighter. But that comparison misses an important part of monetary transmission in a small open economy: the exchange rate.
A higher Australian dollar makes imports cheaper and Australian production relatively more expensive. It lowers imported inflation and shifts demand away from domestic production. A lower dollar works in the opposite direction.
The difficulty is that the Australian dollar moves for many reasons besides monetary policy. Commodity prices are particularly important. A high dollar during a commodity boom does not necessarily tell us that Australian monetary policy is unusually tight.
So can we separate the two?
I estimated a simple long-run relationship between Australia's real trade-weighted exchange rate and commodity prices. The residual gives us a way of asking a useful question: is the Australian dollar unusually expensive or cheap given the commodity prices Australia faces?
The answer produces an interesting history of Australian monetary conditions. It also helps explain how a cash rate of 1.5 per cent could have been too tight in 2017, while a cash rate of 4.6 per cent today does not, by itself, tell us how tight monetary policy is.