Who controls the interest rates?
Prior to the Reserve Bank of Australia (RBA) taking over the responsibility of setting the official cash rate in the late 1980s. The Commonwealth Bank of Australia (CBA) set the cash rate and market competition starting point. However, the CBA did not publish official cash rate figures in the way that the RBA does today. Instead, it set the interest rates on its loans and deposits, and these rates influenced the overall level of interest rates in the economy. https://www.rba.gov.au/about-rba/history/.
Here is a short list of the other highest documented interest rates prior to this that the CBA offered both on its loans and deposits during the early 1980s:
1. 21.0% in November 1981
2. 20.5% in June 1982
3. 20.0% in October 1981
4. 18.5% in March 1982
5. 17.0% in August 1980
It's worth noting that these rates were not directly comparable to the cash rates that the RBA sets today, as they reflect the interest rates on loans and deposits offered by a single bank rather than the overall level of interest rates in the economy. Because of this, this summary offered is on numbers where both economies were RBA controlled, so we focused on the 17% rate height of 1989-90.
1983-84 summary of position.
Data from 1984 is hard to find, but times were tough then too. But still nothing like now. Here are some data summaries for those interested. https://www.ausstats.abs.gov.au/ausstats/free.nsf/0/E00AE4C513B1F1C8CA25750C001332DA/$File/63020_JUN1982.pdf
https://www.finder.com.au/owning-a-home-in-the-80s-vs-today
https://library.bsl.org.au/jspui/bitstream/1/233/1/NATSEM%20Discussion%20Paper%20No_21.pdf