Australian rates of imprisonment are likely to be similar to US imprisonment rates. These were more or less static at Federal, County and State levels from 1925 up until about 1975. After that the rates of imprisonment rose rapidly from about 20/100,000 to 80/100,000 of population for Federal prisoners; from 80/10,000 to 250/100,000 for County or Local prisoners; and from 80/100,000 to 450/100,000 for state prisoners by 2008. After that time, probably due to more leniency and the cost of incarceration there has been a small dip in the rates. But the rates of imprisonment have correlated heavily with changing ethnic make-up of the populations as they have become less European. The cost of maintaining prisons is similar to the costs of a productive, unskilled workforce: “The fee to cover the average cost of incarceration for Federal inmates in Fiscal Year 2014 was $30,619.85 ($83.89 per day). (Please note: There were 365 days in FY 2014.) The average annual cost to confine an inmate in a Residential Re-entry Center for Fiscal Year 2014 was $28,999.25 ($79.45 per day).” (from “The Daily Journal of the US Government” Annual Determination of Average Cost of Incarceration: A Notice by the Prisons Bureau on 03/09/2015).
It is more difficult to find information for a similar period for Australia, but according to the Australian Bureau of Statistics, “between 1999 and 2009, the number of women prisoners increased by 57% compared with a 35% increase in male prisoners for this same period,” where 20% were born overseas in 2009, and 25% of the prison population was indigenous (4517.0 – Prisoners in Australia, 2009).