A new report released by the Australian Institute of Health and Welfare says the rate of Indigenous youth imprisonment has fallen over the last four years.

The report, Youth Detention Population in Australia 2015, shows an overall drop in Indigenous youth on an average night from over 1,000 to fewer than 900.

The four year study shows no real trend in Victoria, and rates of Indigenous youth have increased in Queensland and the Northern Territory while all other states and territories have shown a clear decrease.

David Braddock from the Institute says the rate of Indigenous youth in detention who are awaiting sentencing has not dropped while the rate of sentencing has decreased.